Changed condition indicator

ABSTRACT

A system and method for indication of temperature exposures beyond a set of predetermined limits employs the salts of weak acid-strong base or of a strong acid-weak base compound as reactants. A device includes a housing and capsule. A first reactant and a liquid are included within the capsule. The liquid is chosen such that it expands upon freezing. The capsule is sized such that when the liquid freezes and expands, the capsule fractures. A second reactant is provided within the housing. The location of the second reactant and the method of attaching (if any) the second reactant to the housing may take various forms. When the liquid within the capsule freezes, it expands and fractures the capsule. Upon thawing, the reactant within the capsule escapes and mixes with the reactant located outside the capsule. A second embodiment is a time-temperature indicator. A flexible housing is used, allowing the user to manually deform the housing to fracture a capsule enclosed therein. The reactants combine to produce a color. The color is chosen to be a different color than the housing, allowing a person viewing the indicator device to quickly and easily determine the status of the object being monitored. The threshold temperature at which the device will indicate a changed condition may be varied. Exemplary temperatures include below the freezing temperature, at the freezing temperature, and above the freezing temperature. The capsule composition may be varied such that it melts at a predetermined temperature. Thus, the device may also be used to indicate whether a high temperature has been met or exceeded.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a Continuation-in-Part of U.S. Pat. No. 7,011,037 entitled Changed Condition Indicator issued Mar. 14, 2006, which is a Continuation-in-Part of U.S. Pat. No. 6,694,913 entitled Changed Condition Indicator which issued on Feb. 24, 2004.

FIELD OF THE INVENTION

This invention relates to an indicating apparatus and more particularly, to devices for indicating a change in temperature.

BACKGROUND OF THE INVENTION

In the preparation and storage of foodstuffs, both raw and cooked, it is desirable to have some manner of indicating whether frozen items have previously been thawed. This is true in both home and commercial (such as a grocery store, supermarket, or restaurant) settings. Such information is useful from health, safety, and nutritional standpoints.

In the healthcare industry, it is well known that some vaccines, blood, various medications, etc. are temperature-sensitive. Because such materials may not function properly if frozen and then thawed, it is not only desirable but also essential to know whether these materials have been previously frozen. Similarly, it would be very beneficial to know whether material, which is stored frozen, is allowed to thaw and subsequently is refrozen. Furthermore, it would be very beneficial to know whether material has been cooled below and then heated above a threshold temperature other than the freezing temperature (i.e., above or below the freezing temperature).

It is also desirable in the foodstuff, medical, and other industries to know whether material has been raised above a certain temperature. For example, some vaccines are known to not function properly if stored above a certain temperature. Thus, it would be beneficial to know whether stored material has previously been heated above a predetermined temperature.

Maximum-minimum thermometers may be used to indicate the range of temperatures to which an item has been exposed. However, the use of such apparatus with every item in a frozen food department of a grocery store or supermarket, or with every container of vaccine, blood, drug, or other heat fragile item, is both impracticable and prohibitively costly.

Freeze-thaw indicators are known. For example, the Applicant's previous patent, U.S. Pat. No. 4,163,427, which is incorporated by reference herein in its entirety, discloses an apparatus in which melting ice is used to activate a dye formation in producing a color indication of thawing. The present invention uses a pigment rather than a dye to indicate a transition over the threshold temperature. The use of a pigment allows for a greater clarity of indication, a reduced chance of error, and a reduction in manufacturing costs.

Another known device is marketed under the name “ColdMark Freeze Indicators.” This device comprises three liquids that provide a color change upon extended exposure below a certain temperature and another color change upon extended exposure above the temperature. However, this device is much larger than, and much more expensive than, the device of the present invention.

SUMMARY OF THE INVENTION

The present invention is a system and method for indication of temperature exposures beyond a set of predetermined limits employs the salts of weak acid-strong base or of a strong acid-weak base compound as reactants.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete understanding of the present invention may be obtained from consideration of the following description in conjunction with the drawings in which like reference characters reference like elements, and wherein:

FIG. 1 is a perspective view of a preferred embodiment of the indicator of the present invention;

FIG. 2 is a top view of the indicator of FIG. 1 indicating a safe condition;

FIG. 3 is a top view of the indicator of FIG. 1 indicating a transition from a temperature below the threshold temperature to a temperature above the threshold temperature;

FIG. 4 is a sectional view of the indicator of FIG. 1 taken along line 4-4;

FIG. 5 is a sectional view of another preferred embodiment of the indicator of the present invention;

FIG. 6 is a sectional view of another preferred embodiment of the indicator of the present invention;

FIG. 7 is a sectional view of another preferred embodiment of the indicator of the present invention; and

FIG. 8 is a sectional view of another preferred embodiment of the indicator of the present invention.

DETAILED DESCRIPTION OF VARIOUS ILLUSTRATIVE EMBODIMENTS

The present invention is present invention is a system and method for indication of temperature exposures beyond a set of predetermined limits. The apparatus of the present invention indicates a temperature transition condition using two reactants that combine to produce a pigment. A pigment is insoluble in the medium in which it is applied, while a dye is soluble. The use of a pigment is superior to the use of a dye since, for example, a pigment can produce a more brilliant color with smaller amounts of each reactant.

Additionally, pigment reactants are less likely to produce a color change with anything other than the complementary reactant.

A housing is provided, with one or more capsules are provided within the housing. As used herein, “capsule” refers to any closed receptacle and includes microcapsules. A first reactant and a liquid are provided inside the capsule. The liquid is chosen such that it expands upon freezing. The capsule is designed such that when the liquid freezes and expands, the capsule fractures. A second reactant is provided within the housing. The location of the second reactant and the means of coupling (if any) to the housing may take various forms. For example, the second reactant may take the form of a coating on the housing. The second reactant may also be mixed with an adhesive for coupling the second reactant to the housing. The second reactant may also take the form of a coating on the outside of the capsule. The second reactant may be coupled to a piece of material, such as paper, and the material placed inside the housing.

When the capsule and the liquid located therein freeze, the liquid expands. Since the capsule does not expand upon freezing, the expansion of the liquid fractures the capsule. When the capsule is subsequently thawed, the liquid melts, releasing the first reactant. The first and second reactants then combine to form a pigment. The pigment is a brilliant color that is chosen to be a different color than the housing, allowing a person viewing the changed condition indicator device to quickly and easily know whether the device has been previously frozen and thawed.

The device of the present invention may also be used as a high temperature indicator, either alone or in conjunction with the low temperature indicator embodiment as a dual indicator. The composition of the capsules may be altered such that the capsules will melt at a predetermined high temperature. When the capsules are raised to this temperature, they melt, releasing the enclosed reactant. The reactants then mix, forming a pigment.

The device of the present invention may be attached to any number of items in order to determine whether the temperature of items has been allowed to increase above a threshold temperature. Exemplary threshold temperatures include the freezing temperature and a temperature above which the item being monitored will be rendered ineffective. Exemplary preferred items to monitor include, but are not limited to, vaccines, other medications, food, and other temperature-sensitive items.

The device of the present invention may also be initiated manually. Rather than fracture via expansion upon freezing, the device of the current invention can be initiated by manually fracturing the capsule, thus allowing the device to be used as a time-temperature indicator.

The present invention present invention system and method for indication of temperature exposures beyond a set of predetermined limits involves two or more reactants which produce an irreversible color change when a thermal threshold is crossed. One or more of the reactants are incorporated in microcapsules and one or more of the reactants are in a coating, gel, or solution which is in direct contact with the microcapsules.

The microcapsules can be composed of paraffin wax, wax blends, natural plastics, synthetic resins, as well as a variety of other suitable compatible materials. The microcapsules have an interior variable volume and are of such size that the ratio of the interior volume to capsule wall volume can vary to provide proper mechanical and handling properties while meeting the thermal criteria requirements. Almost any shape or form of container can be used to seal the co-reactant systems together with the microcapsules.

Many of the reactants can be used for both high temperature conditions as well as low temperature conditions depending on the co-reactants used as coatings, gels and solvents which are in contact with the microcapsules.

One embodiment of the present invention present invention system and method for indication of temperature exposures beyond a set of predetermined limits employs the salts of weak acid-strong base or of a strong acid-weak base compound as reactants. When used together with different co-reactants and with different capsule walls to give both high temperature and low temperature indications with the same salt compound.

By varying the specific reactants, microcapsule wall compositions, and the specific design of the enclosure, a series of simply manufacturer items which indicate low temperature threshold, high temperature threshold, low and high temperature threshold, as well as exposure time temperature threshold can be manufactured on one type of machine.

An exposure time temperature threshold indicator is implemented using a whole series of enzymatic reactions and substrates together with flexible containers in conjunction with the microcapsule technique to separate the enzymes from the substrate until activated by bursting.

By incorporating together with the reactants, non-reactive colorless UV (Ultra Violet) fluorescing compounds within the walls of the microcapsules, the body of the container or both, a method of anti-counterfeiting protection is provided.

To more completely understand the range of reactants and indicators that can be used and incorporated into the present invention present invention system and method for indication of temperature exposures beyond a set of predetermined limits, tables 1 through 7. Table 1 represents alkali-metals, corresponding water soluble salts, resultant inorganic precipitants, and color of the precipitant. TABLE 1 PRECIPITANTS. Alkali- Inorganic precipitants Color of Metals Water Soluble Salts *water soluble Product Potassium KOH; KC₂H₃O₂; tests for potassium (#19) K₂Al₂O₄•3H₂0; 1)*Sodium cobaltinitrite 1)yellow KBOC₄H₄O₆•½H₂O; K₂AsO₄; (solid) KH₂AsO₄; KAsO₂; K₂HAsO₄; 2)*Sodium cobaltinitrite 2)yellow KAuCl₄; K₂B₄O₇•H₂O; KBr; (solid) and *silver KBrO₃; K₂PtBr₆; K₂CO₃; nitrate KHCO₃; KCl; KClO; KClO₃; 3)*Dipicrylamine 3)red KClO₄; K₂CrO₄; K₂Cr₂O₇; 4)*sodium 4)white KCN; KCNO; KAg(CN)₂; tetraphenylborate K₃Fe(CN)₆; K₄Fe(CN)₆•3H₂O; 5)all other tests are for 5)See KF; KBF₄; 3KF—AlF₃; KI; KI₃; the various water soluble individual KIO₃; KIO₄; KMnO₄; salts of the particular elements in the K₂MNO₄; K₂MoO₄; KNO₂; elements involved as water soluble KNO₃; K₂C₂O₄•H₂O; KOH; indicted in the other salts column KH₂PO₄; K₄P₂O₇; K₂HPO₃; tables for that element K₃PO₄; K₂SiO₃; K₂SeO₄; K₂S₅; K₂SO₃;•2H₂O; KHSO₄; K₂SO₄; K₂S₂O₅; K₂S₂O₇; K₂S₂O₈; KCNS; K₂C₄H₂O₆•½H₂O; K₂WO₄•2H₂O; KReO₄. Rubidium RbCO3; RbHCO3; Rb2CO3; 1)*LiDipicrylaminate 1)red (#37) RbCrO4; Rb2CrO4; RbF; 2)*AuBr₃ + *H₂PtBr₆ 2)black-brown RbBr; RBrO3; RbCl; RbI; 3)*Na₂AgBi(NO₂)₆ 3)yellow RbIO3; RbOH; RbNO3; Rb2S; RbSO4; Rb2 Cesium CsF; CsBr; CsBRO₃; CsCl; 1)*AuBr₃ + *H₂PtBr₆ 1)deep black (#55) CsClO₃; CsClO₄; CsI; CsIO₃; 2)*Potassium-bismuth 2)orange- CsNO₃; Cs₂CO₃ iodide yellow 3)*AuCl₃ + PdCl₂ 3)black-brown 4)*Sodium 4)black-brown triphenyl(cyanoborate) Lithium LiC₂O₄; LiC₂H₂O₂•2H₂O; 1)Thoron 1)yellow (#3) LiHCO₃; LiBr; LiBrO₃; LiCL; 2)*Complex ferric 2)yellow-white LiClO₃; LiClO₄; LiI; LiIO₃; periodate LiHPO₃; LiNO₂; LiNO₃; LiOH; LiSCN; Li₂CO₃; Li₂S; Li₂SO₄; Li₂SiO₃; Li₃(PO₄)₃ Sodium NaC₂H₃O₂; Na₂C₂O₄; NaAlO₂; tests for sodium (#11) Na₃AsO₄•12H₂0; 1)*Zinc uranyl acetate 1)yellow Na2HAsO₄•12H₂O; 2)*Zinc uranyl acetate 2)green-yellow Na₂HAsO₃; NaBO₂; in ultraviolet light. fluorescence Na₂B₄O₇•10H₂O; NaBr; 3)Alpha- 3)white NaBrO₃; NaCO₃•H₂O; Methoxyphenylacetic Na₂CO₃•10H₂O; NaHCO₃; acid NaCl; NaClO•2.5H₂O; 4)*Magnesium 8-amino- 4)dark grey NaClO₂; NaClO₃; NaClO₄; 1- NaPtCl₄•4H₂O; naphthalenesulfonate Na₂PtCl₆•6H₂O; 5)5- 5)orange- Na₂CrO₄•10H₂O; benzamidoanthroquinone- yellow Na₂Cr₂O₇•2H₂O; NaCN; 2-sulfonic acid NaCu(CN)₂; NaFe(CN)₆•H₂O; 6)*potassium croconate 6)red NaFe(CN)₆•10H₂O; all other tests are for the See the table Na₂Fe(CN)₅NO•2H₂O; various water soluble for the NaCbO₃; NaF; salts of the particular individual 3NaF-AlF₃; NaCHO₂; NaI; elements involved as elements in the NaIO₃; NaIO₄; indicated in the other water soluble NaMnO₄•3H₂O; tables for those elements salt column. Na₂MnO₄•10H₂O; Na₂MoO₄; NaNO₂; NaNO₃; NaOH; Na₂C₂O₄; NaH₂PO₂•H₂O; NaHPO₃•5H₂0; NaH₂PO₄•H₂O; Na₂HPO₄•12H₂O; Na₂PO₄•12H₂O; Na₃PO₄; Na₄P₂O₇•10H₂0; NaKCO₂, 6H₂O; NaReO₄; Na₂SeO₃; NaSeO₄; NaSiO₃; Na₂Si₄O₉; NaSn(OH)₄; Na₂S; Na₂S₅; Na₂SO₃; Na₂S₂O₃•5H₂O; NaHSO₄; Na₂SO₄; Na₂SO₄•10H₂O; Na₂S₂O₅; NaCNS; Na₂C₄H₄O₆•2H₂O; Na₃VO₄; Na₂WO₄;

Table 2 represents alkali earth metals, corresponding water soluble salts, resultant inorganic precipitants, and color of the precipitant. TABLE 2 Alkali PRECIPITANTS. Earth Inorganic precipitants Color of Metals Water Soluble Salts *water soluble Product Beryllium BeBr₂; BeCl₂; BeI₂; 1)Quinalizarin; 1)blue (#4) Be(ClO4)2; 2)p-Nitrobenzeneazoorcinol; 2)orange-red Be(NO₃)₂•3H₂O; 3)*Beryllon = [tetrasodium 2-(3,6- 3)light blue BeC₂O₄•3H₂O; disulfo-8-hydroxynaphthylazo)- BeSO₄•4H₂O 1,8-dihydroxynaphthalene-3,6- disulfonate] = (Beryllon II); 4)Chrome Azural S; 4)blue-violet 5)Chrome Azural S + Cetyltrimethylammonium 5)blue bromide; 6)Erichrome Cyanine R; 6)red 7)Erichrome Cyanine R + Cetyltrimethylammonium 7)red bromide 8)Morin 8)green-yellow fluorescence Magnesium Mg(C₂H₃O₂)₂•4H₂O; 1)*Alkali hypoiodite; 1)brown (#12) MgBr₂, 2)Quinalizarin; 2)blue MgCl₂•6H₂O; MgI₂, 3)p-Nitrobenzeneazo-alpha- 3)blue Mg(NO₃)₂•6H₂O; naphthol; MgSO₃; 4)Titan Yellow; 4)flame red MgSO₄•7H₂O; 5)p-Nitrobenzeneresorcinol. 5)blue Mg(BrO₃)₂; 6)Eriochrome Black T 6)? Mg(ClO₃)₂; 7)8-Hydroxyquinoline 7)? Mg(ClO₄)₂; 8)8-Hydroxyquinoline + Butylamine 8)? Mg(IO₃)₂; Butylamine MgCr₂O₇; 9)Xylidyl Blue 9)purple Mg(NO₂)₂; 10)Chromotrope 2B 10)blue MgS₂O₃. 11)*pentamethinedibarbituric acid 11)blue 12)*Ammonia + phenolphthalein 12)pink 13)Diphenylcarbizide 13)deep red Calcium Ca(C₂H₃O₂)₂•H₂O; 1)Chlorophosphonazo III; 1)? (#20) CaBr₂; CaCl₂•6H₂O; 2)Glyoxal-bis(2hydroxyanil); 2)blue Ca(ClO3)₂•4H₂O; 3)Murexide; 3)? Ca(ClO₄)₂; CaI2; 4)Phthalein Purple; 4? Ca(IO3)2; CaCrO_(4;) 5)*Ammonium ferrocyanide, 5)white Ca(NO2)2; 6)*Dihydoxytartaric acid osazone 6)white flock Ca(NO₃)₂•4H₂O, (solid) Ca(MnO₄)₂•4H₂O, 7)*Sodium rhodizonate. And 7)violet Ca(H₂PO₂)₂; CaSO4; alkali hydroxide CaSeO₄•2H₂O 8)Chloroindazone C 8)red-violet 9)*Ferric fluoride and *potassium 9)red thiocyanate 10)Alizarin Red S and *Zirconium 10)red-violet oxychloride 11)Calcichrome 11)blue Strontium Sr(OH)_(2;) 1)*Sodium rhodizonate. 1)red-brown (#38) SrBr₂•6H₂O; Sr(BrO₃)₂; SrCl₂•6H₂O, Sr(ClO₂)_(2;) Sr(ClO₃)₂; SrI₂•6H₂O; Sr(IO₃)₂; Sr(NO₂)₂•4H₂O; Sr(NO₃)₂; SrS₂O₅. Barium BaO; Ba(OH)₂;, 1)*Sodium rhodizonate; 1)red-brown (#56) BaBr₂•2H₂O, 2)Tetrahydroxyquinone + KCl; 2)red (acid) Ba(BrO₃)₂; 3)*Sulfonazo III 3)blue-green BaCl₂•2H₂O; 4)*Induction of precipitation of 4)white Ba(ClO₂)₂; lead sukfate Ba(ClO₃)₂•2H₂O; 5)*Potassium permanganate and 5)violet Ba(ClO₄)₂, BaI₂, *sodium sulfate Ba(NO₂)_(2;) 6)Nitro-3-hydroxybenzoic acid 6)red ring Ba(NO₃)₂; Ba(MnO₄)_(2;) BaH₄(PO₄); BaS; Ba(SCN)₂; BaC₂O_(4;) Ba(C₂H₃O₂)•2H₂O.

Table 3 represents transition elements, corresponding water soluble salts, resultant inorganic precipitants, and color of the precipitant. TABLE 3 PRECIPITANTS. Transition Inorganic precipitants Color of Element Water Soluble Salts *water soluble Product Fourth Row Scandium ScCl₃, ScBr₃, Scl₃, 1)Tetrahydroxyflavanol 1)green (#21) Sc₂(SO₄)₃, Sc(NO₃)₃ (“Morin”); flourescence 2)*Alizarin red S; 2)?; 3)*Xylenol Orange; 3)?; 4)Arsenazo III; 4)?; 5)Chrome Azural S. 5)?. 6)Methylthymol Blue 6)deep blue Titanium TiCl₂; TiCl_(3.;) TiCl₄ 1)*Pyrocatechol, 1)yellowish- (#22) TiK₂F₆, red Ti₂(C₂O₄)₃•10H₂O, 2)*Chromotropic Acid; 2)brown-red TiO(C₂O₄K)₂•2H₂O, 3))*Chromotropic Acid + conc. 3)violet Ti(SO₄)₂•9H₂O, *Sulfuric acid TiOSO₄•H₂SO₄•8H₂O 4)*Tiron; 4)orange-red 5)*Hydrogen peroxide; 5)yellow 6)*Tannin + antipyrine; 6)red 7)Diantipyrinylmethane. 7)? 8)*Methylene blue and zinc. 8)discharge of methylene blue 9)Acetylacetone 9)Ti (III) - red Ti (IV) - yellow 10)Morin 10)brown 11)*Alizarin Red S and zinc 11)green 12)Resoflavine 12)red-orange 13)Tetraphenylarsonium 13)yellow chloride 14)Tetraphenylphosphonium 14)yellow chloride 15)Benzyl 2-hydroxyphenyl 15)yellow ketone 16)Ammonium hypophosphite melt 16)blue Vanadium Na(C₆H₁₄O₃)₂V(CO)₆*, 1)*Cacotheline; 1)violet (#23) V₂O₂Cl₄•5H₂O, 2)8-Hydroxyquinoline; 2)blue-black VOSO₄•2H₂O, VCl₂, 3)Aniline; 3)aniline black VCl₃, VCl₄. 4)Phosphomolybdic acid; 4)molybdenum blue 5)*Hydrogen peroxide; 5)red-brown to blood red. 6)N-Benzoyl-N- 6)? phenylhydoxylamine; 7)4-(2-pyridylazo)resorcinol. 7)? 8)*Reduction of ferric salts by 8)red tervalent vanadium 9)alpha-Benzoinoxime 9)yellow 10)3.3′-Dimethylnaphthidine 10)blue-violet 11)Quercetin 11)green 12)2-(salicylideneimino)benzoic 12)violet acid 13)Sulphosalicylic acid and 13)blue *phosphoric acid 14)*Koji acid 14)red-brown 15)*8-Hydroxy-7-iodoquinoline- 15)green 5-sulfonic acid (“Ferron”) 16)Resorcinol and *syrupy 16)deep blue phosphoric acid (fluoresces red under U, V,) 17)*Ammonium hypophosohite 17)green melt Chromium Cr(C₂H₃O₃)₃•H₂O, 1)1,5-Diphenylcarbizide (for 1)violet (alk.) (#24) CrO₃, chromates, alkaline); to red CrCl₃•6H₂O, 2)4-(2-Pyridylazo)resorcinol; 2)? CrF₃•4H₂O, CrF₃•9H₂O, 3)4-(2-Pyridylazo)resorcinol + *Tetradecyldimethylbenzyl- 3)? Cr(OH)(HCOO)₂, ammonium chloride; CrF₃•9H₂O, 4)*Acetic acid Benzidine (for 4)blue Cr(OH)(HCOO)₂, chromates) solution; Cr(NO₃)₃•9H₂O, 5)Acid Alizarin RC; 5)orange lake Cr(NO₃)₃•9H₂O, 6)*Silver nitrate (for chromates); 6)red CrSO₄•7H₂O, 7)*Lead acetate (for chromates); 7)yellow Cr₂(SO₄)₃•15H₂O, 8)4-(2-Pyridylazo)resorcinol + *Hydrogen 8)? Cr₂(SO₄)₃•18H₂O, peroxide. CrNH₄(SO₄)₂•12H₂O, 9)Chromotropic acid 9)brown-red CrK(SO₄)₂•12H₂O, 10)1,2-diaminocyclohexane- 10)reddish- CrBr₂, CrCl₂, CrCL₃, N,N,N′N′-tetraacetic acid violet CrC₂O₄•H₂O, 11)Diphenylcarbizide + phthalicanhydride 11)violet 12)2,7-Diamino-diphenylene 12)blue oxide 13)Sel-K5 exchange resin 13)red- violet(Cr⁺⁶) 14)*Hydrogen peroxide + cation 14)gray, violet- exchange resin(Amberlite blue, IRA-4II [Cl— form 30 mesh) or violet brown 15)Methyl violet 15)deep blue 16)Pyrrole 16)“pyrrole blue” 17)Strychnine 17)blue-violet to red 18)Ammonium hypophosphite 18)green melt Manganese Mn(C₂H₃O₂)₂•4H₂O, 1)*Formaldioxime hydrochloride; 1)orange-red (#25) MnSO₄•(NH₄)₂SO₄•6H₂O, 2)a)*Periodate; 2)a)violet MnSO₄•(NH₄)₂SO₄•6H₂O, b)*Periodate + tetrabase; b)blue Mn₃(C₆H₅O₇)₂, 3)Alkali hydroxide + benzidine; 3)blue MnS₂O₆, 4)*Ammoniacal silver nitrate 4)black Mn(C₆H₁₁O₇)₂•2H₂O, 5)Sodium perxenate(solid) 5)violet to pink CH₂OHCHOHCH₂OP(O)O₂Mn, 6)Benzidine 6)blue Mn(H₂PO₂)•H₂O, 7)*Tollens reagent 7)black Mn(C₃H₅O₃)₂•3H₂O, 8)Lead dioxide 8)violet MnBr₂, MnCl₂, MnCl₂•4H₂O, Mn(IO₃)₂; Mn(NO₃)₂•6H₂O, MnSO₄•5H₂O, Mn₂O₇ Iron (#26) Ferric ammonium 1)*8-hydroxyquinoline-7-iodo-5- 1)green citrate, sulfonic acid; (NH₄)₃Fe(C₂O₄)₃•3H₂O, 2)Potassium ferrocyanide; 2)prussion blue FeNH₄(SO₄)₂•12H₂O, 3)Alpha,alpha′-Dipyridyl; 3)deep red ferric ammonium 4)Potassium thiocyanate; 4)deep red tartrate, FeF₃, FeBr₂, 5)Dimethylglyoxime 5)red FeCl₂, FeCl₃, 6)*Sodium dimethylglyoxime 6)red Fe(ClO₄)₂, 7)*Disodium-1,2- 7)pH <5 deep Fe[(CH₃)₂AsO₂]₃, dihydroxybenzene-3,5- blue, pH 5.7 to FeC₆H₅O₇•2H₂O, disulfonate; 6.5 violet, Fe₂(Cr₂O₇)₃, pH7red. Fe[C₃H₅(OH)₂PO₄]₃•xH₂O, 8)*Thioglycolic acid; 8)purple-red Fe₂(C₄H₄O₅)₂, 9)*Quercitrin; 9)olive green Fe(NO₃)₂, 10)*2-Nitroso-1-naphthol-4 10)green Fe(NO₃)₃•9H₂O, sulfonic acid. FeSO₄, Fe₂(C₂O₄)₃, 11)*Sodium Phosphate; 11)Yellow- ferric potassium citrate, white ferric pyrophosphate 12)Bathophenanthroline; 12)red soluble (A combination 13)* Bathophenanthroline 13)red of ferric pyrophosphate disulfonic acid; (Fe₄(P₂O₇)₃•xH₂O) and 14)Ferene; 14)? sodium citrate). 15)Chrome Azurol S + *Cetyltrimethylammonium 15)? bromide; 16)1,10-Phenanthroline; 16)red 17)1,10-Phenanthroline + Bromothymol 17)? Blue; 18)*Ferrozine 18)? 19)Isonitrosobenzoylmethane 19)blue 20)Phenyl 2-pyridyl ketoxime 20)violet 21)Pyridine-2,4,6-tricarboxylic 21)purple acid 22)5,7-Dibromo-8- 22)green-black hydroxyquinoline 23)Quercetin or quercitin 23)olive-green 24)Alpha-Furil monoxime 24)red 25)p-Amino-N,N-dimethylaniline 25)rose 26)o-Phenylenediamine 26)yellow to red Cobalt (#27) Co(C₂H₃O₂)₂•4H₂O, 1)Alpha-nitroso-beta-naphthol; 1)red-brown CoSO₄•(NH₄)₂SO₄•6H₂O, 2)Beta-Nitroso-alpha-naphthol; 2)red-brown CoBr₂•6H₂O, CoCl₂,, 3)Rubeanic acid; 3)yellow- CoCl₂•6H₂O, brown Co(ClO₄)₂, 4)*Ammonium Thiocyanate and 4)deep blue CoF₂, Co(CHO₂)₂•2H₂O, acetone; CoI₂•6H₂O, Co(NO₂)₂, 5)*2-Nitroso-1-naphthol-4- 5)red Co(NO₃)₂, sulfonic acid. CoSiF₆•6H₂O, CoSO₄, 6)*Nitroso R salt; 6)red CoSO₄•7H₂O, 7)4-(2-Pyridylazo)resorcinol; 7)? K₃Co(NO₂)₆, 8)4-(2-Pyridylazo)resorcinol + Diphenylguanidine; 8)? Co(SCN)₂ 9)*Sodium thiosulfate 9)blue 10)Chromotropic acid dioxime 10)blue 11)*Sodium 11)greenish- pentacyanopiperidine ferrate blue 12)*Hydrogen peroxide and 12)green *sodium bicarbonate 13)*Mangabous sulfate & 13)brown butyraldehyde 14)*Sodium azide & o-tolidine 14)blue 15)Diacetylmonoxime p- 15)violet or nitrophenyl-hydrozone purple 16)3-Hydroxyiminopentane-2- 16)red one p-nitrophenylhydrozone 17)Ammonium hypophosphite 17)blue melt Nickel (#28) Ni(OOCCH₃)₂•4H₂O, 1)Dimethylglyoxime; 1)Red ppt. NiF₂, NiCl₂•NH₄Cl, 2)*Sodium Dimethylglyoxime; 2)Red ppt; Ni(ClO₄)₂, 3)Dimethylglyoxime and 3)Red to NiCl₂•NH₄Cl•4H₂O, bromine water; orange NiBr₂, NiBr₂•3H₂O, 4)Rubeanic Acid (dithiooxamid); 4)blue to blue NiCl₂, NiCl₂•6H₂O, violet; NiI₂, 5)2,2′-Furildioxime; 5)? (HCOO)₂Ni•2H₂O, 6)2-(5-Bromo-2-pyridylazo)- 6)? Ni(NO₃)₂•6H₂O, diethylaminophenol; Ni(NO₃)2, 7)2-(2-Pyridylazo)-2-naphthol; 7)? Ni(NO₃)₂•4NH₃•2H₂O, 8)4-(2-Pyridylazo)resorcinol; 8)? NiSO₄•K₂SO₄•6H₂O, 9)*4-(2-Pyridylazo)resorcinol 9)? NiSO₄•6H₂O, sodium salt; NiSO₄•7H₂O; 10)Quioxaline-2.3-dithiol 10)red Ni(SCN)₂ Copper Cu(C₂H₃O₂)₂•H₂O, 1)Benzoin oxime 1)green (#29) CuBr₂, CuCl₂, 2)* 4)Salicylaldoxime; 2)yellow-green CuCl₂•2H₂O, 3)o-Tolidene and *ammonium 3)light to dark Cu(ClO₄)₂, thiocyanate; blue CuCr₂O₇•2H₂O, 4)*Phosphomolybdic acid; 4)deep blue CuSiF₆•4H₂O, 5)*1,2-Diaminoanthraquinone 5)blue [CH₂OH(CHOH)₄COO]₂Cu, sulfonic acid; Cu(C₃H₅O₃)₂•2H₂O, 6)Rubeanic acid; 6)black Cu(NO₃)₂•3H₂O, 7)Dithizone; 7)yellow- Cu(NO₃)₂•6H₂O, brown [C₆H₄(OH)SO₃]₂Cu•6H₂O, 8)Benzidine + *potassium 8)blue CuCl₂•2NaCl•2H₂O, bromide; CuSO₄•5H₂O, 9)p-Dimethylaminorhodanine; 9)red Cu(NH₃)₄SO₄•H₂O, 10)8-hydroxyquinolline + *potassium 10)red CuSeO₄ cyanide; 11)*Ammonium mercury 11)violet thiocyanate + *zinc salts; 12)*Hydrobromic acid; 12)violet to brown. 13)*2-Nitroso-1-naphthol-4- 13)orange(pH sulfonic acid. 7-8) 14)Phennetidine + hydrogen 14)violet peroxide; 15)Diphenylcarbazone; 15)violet 16)Di-m-nitrophenylcarbazone; 16)violet 17)Bathocuproine; 17)? 18)* Bathocuproine disulfonic 18)? acid; 19)Neocuprine; 19)? 20)Cuprizone 20)? 21)*Potassium ferrocyanide 21)brick red 22)Zinc ferrocyanide 22)brick red 23)*Sodium 23)brown diethyldithiocarbamate 24)Zinc diethyldithiocarbamate 24)brown- yellow 25)2,2′-Biquinoyl (Cuproin) 25)purple-red 26)*Catalysis of the ferric- 26)deep violet thiosulfate reaction 27)p-Phenylenediamine & 27)black *ammonium thiocyanate(on Dowex 50-X or 1% DVB) 28)Alizarin Blue 28)cornflower- blue 29)*Ammonium bromide & 29)violet *Concentrated Phosphoric acid 30)Alkali tartrate, *hydrogen 30)indigo blue peroxide & o-hydroxyphenylfluorone 31)Catalysis of the autoxidation 31)brown of resorcinol 32)Benzamiidoxime 32)green 33)Acetylene 33)intense red 34)Lumocupferron 34)green fluorexcence 35)Potassium guaiacol-o-sulfate 35)greenish- yellow 36)8,8′-Diquinolyldisulfide 36)? Zinc (#30) Zn(C₂H₃O₂)₂•2H₂O, 1)*Potassium ferricyanide and 1)yellow to ZnF₂, ZnCl₂•2NH₄Cl, diethyl aniline; brownish red ZnO 45% B₂O₃ 34% 2)Dithizone 2)purple-red may have 20% water of 3)*Potassium ferricyanide + p- 3)blue hydration, phenetidine; Zn(BrO₃)₂•6H₂O, 4)Uranyl ferrocyanide; 4)white on ZnBr₂, brown Zn(ClO₃)₂•4H₂O, 5)Resorcinol. 5)blue ZnCl₂, Zn(ClO₄)₂, Zinc 6)1-(2-Pyridylazo)-2-naphthol 6)? chloroiodide (A 7)*Xylenol Orange 7)? mixture of chloride and 8)Zircon 8)? iodide), 9)*Potassium ferricyanide and 9)dark red- Zn(C₂H₅SO₄)₂•2H₂O, 3.3′-dimethylnaphthidine brown ZnSiF₆•6H₂O, 10)Induced precipitation of 10)blue Zn(HSO₂•CH₂O)₂ Co[Hg(CN)4} (normal), 11)Trisodium pentacyano-p- 11)pale green Zn(CHO₂)₂•2H₂O, Zinc nitroso-dimethylanilino-ferrate(II) to blue gluconate, 12*Potassium cobalticyanide 12)green C₃H₅(OH)₂OPO₃Zn, 13)Vanillinazin 13)dark red ZnS₂O₄, Zn(OH)₂, 14)*Potassiumferricyanide and 14)blue Zn(H₂PO₂)₂•H₂O, ZnI₂, methylene blue Zn(IO₃)₂, 15)*Potassiumferrocyanide, 15)violet Zn(C₃H₅O₃)₂•3H₂O, *thiourea, and Rhodamine B Zn(OOCCH₂CHOHCOO)•3H₂O, 16)*Potassiumferrocyanide and 16)yellow Zn(NO₃)₂•6H₂O, methyl violet Zn(MnO₄)₂•6H₂O, 17)4-aminobenzenethiol 17)rose Zn(SO₃C₆H₄OH)₂•8H₂O, 18)*Potassiumferrocyanide, 18)deep blue Zn(OOC₂H₅)₂, *potassium iodide and starch Zn[C₆H₄(OH)COO]₂•3H₂O, ZnSO₄•7H₂O, ZnSO₄•H2O, Zn(CNS)₂, “Calgon composition TG”(a glassy composition of sodium zinc hexametaphosphate). ZnSeO₄ Fifth Row Ytrium Y(C₂H₃O₂)₃•8H₂O, 1)*Alizarin Red S; 1)? (#39) YBr₃•9H₂O, 2)Arsenzo III; 2)? YCl₃•6H₂O, Y(NO₃)₃ 3)*Xylenol Orange. 3)? 4)Catechol and organic bases 4)white 5)Complex of catechol violet 5)blue with *boric acid Zirconium H₂ZrO₂(C₂H₃O₂)₂ 1)2-Nitroso-1-naphthol; 1)green-yellow (#40) available as 22% and 2)1-Nitroso-2-naphthol; 2)red 13% ZrO₂ aqueous 3)Alizarin; 3)red brown to solutions, Zr(NH₄)₂F₆, dark violet H₄ZrO(CH₃CHOCO₂)₃, 4)p- 4)brown Zr(NO₃)₄•5H₂O, Dimethylaminoazophenylarsonic ZrOCl₂, 8H₂O, ZrK₂F₆ acid; (hot), Zr(SO₄)₂•4H₂O, 5)a)*Carminic acid 5)a)yellow to ZrOOHCl•nH₂O, red, ZrO(OH)NO₃. [or} b)gallocyanine]; b)pink to blue 6)5-Chlorobromoamine acid; 6)red 7)*Alizarin Red S; 7)? 8)Arsenazo III; 8)? 9)*Xylenol Orange. 9)? 10)m-(2-Hydroxynaphthalene-1- 10)pink azo)-mandelic acid Niobium NbO(HC₂O₄)₃•4H₂O, 1)N-Benzoyl-N- 1)? (#41) K₂NbOF₅•H₂O. phenylhyroxylamine; 2)*Pyrocatechol + EDTA; 2)? 3)2,2′-Bipyridil; 3)? 4)1-(2-thenoyl)-3.3.3- 4)? trifluoroacetone; 5)Bromopyrogallol red; 5)? 6)Bromopyrogallol red + Cetylpyridinium 6)? chloride; 7)4-(2-Pyridylazo)resorcinol; 7)? 8)Sulfochlorophenol S; 8)? 9)*Xylenol Orange. 9)? 10)*Pyrpgallol-4-sulfonic acid 10)orange- orange red 11)Ammonium hypoohosphite 11)black melt 12)*Zinc chloride 12)blue-black Molybdenum H₄SiMo₁₂O₄₀•xH₂O x = usually 1)Phenylfluorone; 1)? (#42) 6-8, 2)Bromopyrogallol Red + Cetylpyridinium 2)? Heteromolybdates such chloride; as Na3PMo12O40 (can 3)Toluene-3,4-dithiol, 3)? contain phosphorous, 4)*Potassium thiocyanate + stannous 4)brick red arsenic, iron, and chloride; tellurium as hetero 5)*Potassium xanthate; 5)pink to violet atoms and any of 35 6)*Zinc or *cadmium xanthate; 6)red elements can be 7)Phenylhydrazine; 7)blood red present. The acids and 8)Tincture of cochineal; 8)Flame red most of the salts are fluorescence very soluble, (pH 5.7-6.2) Na2MoO2, 9)Alpha,alpha′-Dipyridil + *stannous 9)violet Na4SiMol2O40, MFP. chloride; 10)Diphenylcarbazide; 10)violet 11)Di-beta-naphthylcarbazone 11)violet 12)*Potassium ethyl xanthate 12)deep red- blue 13)Zinc ethyl xanthate 13)deep red- blue 14)Methylene blue and hydrazine 14)Fading of blue 15)o-Hydroxyphenylf; uorone 15)carmine 16)Morin and butanol 16)brown 17)Ammonium hypophosphite 17)red-brown melt Ruthenium Ru₂(OH)₂Cl₄•7NH₃•3H₂O, 1)1,10-Phenanthroline; 1)? (#44) RuCl₃. 2)*Thiourea; 2)? 3)1,4-Diphenylthiosemicarbazide; 3)? 4)*Potassium chlorate + potassium 4)blue black iodide (+starch); 5)Rubeanic acid; 5)blue 6)Benzidene; 6)blue or green 7)*Potassium ferrocyanide. 7)blue or green Rhodium RhCl₃(if hydrated), 1)1-(2-Pyridylazo)-2-naphthol 1)? (#45) Rh(NO₃)₂•2H₂O, 2)*Stannous chloride + *ammonium 2)cherry red Rh(SO₄)₂•12H₂O, chloride and *potassium iodide Palladium PdCl₂, PdCl₂•2H₂O, 1)*Mercuric cyanide + *Stannous 1)orange-red to (#46) Pd(NO₃)₂, PdCl₂•2KCl, chloride. yellow gold PdCl₂•2NaCl, 2)Nickel dimethylgloxime; 2)pink to red 3)Naphthalene-4′-sulfonic acid-1- 3)orange- azo-5-o-8-hydroxyquinoline; yellow 4)p-Dimethylaminobenzylidene 4)red-violet rhodanine; 5)Diphenylcarbazide and 5)violet *mercuric cyanide; 6)2-(5bromo-2-pyridylazo)-5- 6)? diethylaminophenol; 7)Dithizone; 7)? 8)2-Nitroso-1-Napthol; 8)? 9)4-(2-Pyridilazo)resorcinol 9)? 10)*Mercuric iodide 10)black or grey 11)p-Nitrosophenylamine 11)red or purplish brown 12)Phenooxithine 12)yellow to red brown 13)3-Hydroxy-3-phenyl-1-sulfo- 13)? phenyltriazene 14)Mercaptobenzoindazole 14)orange 15)*Mercuric cyanide and methyl 15)red yellow 16)Parafuchsin 16)brown 17)Alpha-nitroso-beta-naphthol 17)dark-brown 18)Potassium ferrocyanide and 18)red alpha-alpha′-dipyridyl 19)Triphenylstilbene 19)pink to red 20)Voluric acid 20)yellow- brown 21)Ammonium molybdate and 21)blue sodium hypophosphate Silver (#47) AgF•H₂O, AgNO₂, 1)Dithizone; 1)violet AgNO₃, KAg(CN)₂, 2)*Eosin + 1,10Phenanthroline; 2)? Ag₂S₂O₃•2Na₂S₂O₃•2H₂O, 3)Methylthymol blue + *Barium 3)? Ag₂SO₄ (hot), AgClO₂, (II) (Sulfate) AgClO₃, AgClO₄, 4)N,N,-Dimethyl-1,4- 4)? phenylenediamine (Sulfide); 5)Pararosaniline + *Formaldehyde 5)? (Sulfite); 6)*Manganese Nitrate and alkali; 6)black 7)p-Dimethylaminobenzylidene 7)red violet rhodanine; 8)*Potassium Chromate; 8)red 9)*Stannous chloride and 9)black chromotropic acid; 10)*Stannous Chloride 10)free silver 11)*Sodium selenosulfate 11)brown 12)*Persulfate and pyridine 12)yellow 13)1,10-Phenanthroline and 13)blue bromo-pyrogallol red 14)*Cuprous thiocyanate 14)smoke- brown 15)p- 15)red violet Dimethylaminobenzylidenethio- barbituric acid 16)Ethylenediaminetetraacetic 16)black or acid + *FeSo4 + *sodium acetate grey 17)Potassium ferrocyanide and 17)red alpha,alpha′-dipyridyl 18)Potassium nickel cyanide and 18)red dimethylglyoxime Cadmium Cd(OOCCH₃)₂•3H₂O, 1)Dithizone; 1)? (#48) CdF₂, CdBr₂•4NH₄Br, 2)Cadion; 2)? Cd₅(BW₁₂O₄₀)•18H₂O, 3)2-(5-Bromo-2-pyridylazo)-5- 3)? CdBr₂, CdBr₂•4H₂O, diethylaminophenol; Cd(ClO₃)₂•2H₂O, CdCl, 4)4-(2-Pyridylazo)rersorcinol; 4)? CdCL₂•2.5H₂O, 5)Di-p-nitrophenylcarbazide: 5)green-blue Cd(ClO₄)₂,, 6)Ferrous dipyridyl iodide; 6)red-violet CdI₂(alpha), Cd(NO₃)₂•4H₂O, 7)Di-beta-naphthylcarbazone; 7)red to violet Cd(NO₃)₂, 8)Diphenylcarbazide; 8)violet CdI₂•2KI•2H₂O, CdSO₄, 9)p-Nitrodiazoaminoazo benzene 9)bright pink 3CdSO₄•8H₂O, (Cadion 2B) CdSO₄•4H₂O, CdSeO₄ 10)*Sodium Sulfide 10)yellow 11)Zinc Sulfide 11)yellow 12)Glyoxal bis-(2-hydroxyanil) 12)blue 13)*Cyanide and *sodium sulfite 13)yellow 14)Bis-(p- 14)intense ethylbenzylaminophenyl)- crimson antipyrinyl-methanol 15)Dithizone and cyclohexanone 15)orange Sixth Row Lanthanum La(C₂H₃O₂)₃•xH₂O, 1)Arsenzo III. 1)? (#57) La(NO₃)₃ × 2NH₄NO₃ × 4H₂O, 2)Acid Monochrome Bordeaux S 2)orange LaCl₃•7H₂O, La(NO₃)₃•6H₂O. Hafnium HfOCl₂•8H₂O, 1)Arsenzo III. 1)? (#72) K₂HfF₆, HfBr₄, HfCl₄. 2)Arsenzo I 2)red-violet 3)Quercetin and *perchloric acid 3)green fluorescence (UV) Tantalum Na₈Ta₆O₁₉•25H₂O, 1)*Methyl Violet; 1)? (#73) K₂TaF₇(hot). 2)4-(2-Pyridylazo)resorcinol; 2)? 3)Phenylfluorone 3)? 4)Catechol violet 4)blue-violet 5)*Pyrogallol-4-sulfonic acid 5)yellow and *oxalic acid Tungsten See Hetromolybdates 1)*Pyrocatechol Violet; 1)? (#74) for heterotungstates, 2)*Tetraphenylarsonium chloride + *Thiocyanate; 2)? especially 3)Toluene 3,5-dithiol; 3)? phosphotungstates such 4)*Stannous chloride; 4)blue as H₃PW₁₂O₄₀•xH₂O, 5)Diphenylene. 5)white ppt. Na₂WO₄•2H₂O, WCl₅, 6)8-Hydroxyquinoline 6)orange WBr₅, yellow (NH4)₆W₇O₂₄•6H₂O, 7)Ammonium hypophosphite 7)blue K₂WO₄•2H₂O, melt 2(NH₄)₃PO₄•24WO₃•xH₂O, (NH₄)₆H₂W₁₂O₄₀•xH₂O Rhenium Re₂O₇, ReCl₃, ReO₃, 1)2.2′-Furildioxime. 1)? (#75) NaReO₄. 2)*Tris(alpha,alpha′-dipyridyl)- 2)red iron(II)sulfate Osmium OsO₄, (NH₄)₂OsCl₆. 1)1.5-Diphenylcarbazide; 1)? (#76) 2)*Potassium chlorate + potassium 2)blue iodide + starch; 3)*Benzidene acetate; 3)blue or green 4)Potassium ferrocyanide. 4)blue or green 5)3.3′-Dimethylnapthidine 5)red 6)Apomorhine 6)brownish-red 7)p-Phenylenediamine 7)violet-red Iridium IrCl₂, IrCl•xH₂o, 1)Rhodamine 6G + Tin(II); 1)? (#77) IrCl₄•2NH₄Cl, 2)N,N-Dimethyl-4- 2)red Ir₃•3NH₄Cl, nitrosoaniline. Ir₂(SO₄)•3(NH₄)₂SO₄•24H₂O, 3)a)Alizarin or 3)a)dark red, IrCl₄, IrBr₃•4H₂O, b)Quinalizarin b)violet K₂IrCl₆. 4)Benzidine 4)blue Platinum (NH₄)₂PtCl₆, 1)Dithizone; 1)? (#78) H₂PtCl₆•6H₂O, 2)2-Mercaptobenzothiazole; 2)? BaPt(CN)₄•4H₂O, 3)Sulfochlorophenolazorhodamine 3)? PtCl₄, PtCl₄•5H₂O, 4)*Thallium nitrate* + *Stannous 4)yellow to PtCl₄•8H₂O, chloride. orange red Na₂PtCl₄•4H₂O 5)*Alkali iodide 5)brown Na₂PtCl₆•6H₂O, 6)1.4.-Diphenyl-3- 6)green Pt(SO₄)₂•4H₂O, PtI₄. thiosemicarbazide Gold (#79) Au(CN)₃3H₂O,HAu(CN)₄•3H₂O, 1)*Rhodamine B; 1)red-violet NaOOCCH(SAu)CH₂COONa•H₂, 2)5-(4- 2)red-violet AuCl₃, Diethylaminobenzylidene) AuCl₃•2H₂O, rhodanine; AuCL₂•HCl•4H₂O, 3)Benzidene. 3)blue HAuCl₄•4H₂O, 4)Alpha-Naphthylamine and 4)violet NaAuCl₄•2H₂O, butanol NaAu(CN)₂, AuBr₃, 5)N,N′-di-2-naphthyl-p- 5)red-brown HAuBr₄•5H₂O, phenylene-diamine Au₂O₃•2SO₃•H₂O, HAu(NO₃)₄•3H₂O. Mercury Hg(C₂H₂O₂)₂, 1)Diphenylcarbazone); 1)blue or (#80) HgCl₂•2NH₄Cl•2H₂O, violet HgBr₂•BaBr₂, 2)*Xylenol Orange; 2)? HgI₂•BaI₂•5H₂O, HgCl₂, 3)Michler's thioketone; 3)? Hg(CN)₂, HgF₂, 4)*Stannous chloride and 4)grey or black Hg(C₃H₅O₃)₂, aniline; Hg(NO₃)₂•2H₂O, 5)p-Dimethylaminobenzylidene 5)violet Hg(NO₃)₂•½H₂O, rhodanine; HgO•Hg(CN)₂, 6)*Copper(I) iodide; 6) Hg(CN)₂•2KCN, 7)*Chromotropic acid. 7)brown or K₂HgI₄ or 2KI•HgI₂, yellow “merbromin”C₂0H₈Br₂ 8)Dithizone 8)orange HgNa₂O₆, mercurol 9)Potassium ferrocyanide + nitrosobenzene 9)violet (contains 20% or other nitrosos mercury), Hg₂(ClO₃)₂, 10)Chromotropic Acid 10)brown or HgSO₄ yellow 11)Potassium ferrocyanide and 11)red alpha,alpha′-dipyridyl 12)Glyoxal bis-(2-mercaptoanil) 12)dark red to pale pink 13)Ammonium sulfide 13)?

Table 4 represents metals, corresponding water soluble salts, resultant inorganic precipitants, and color of the precipitant. TABLE 4 PRECIPITANTS. Inorganic precipitants Color of Metals Water Soluble Salts *water soluble Product Aluminum Al(ClO₃)₂•6H₂O; 1)*Alizarin Red S; 1)red (#13) Al(ClO₄)₃; AlF₃; 2)*Aluminon; 2)red lake AlCl₃; AlI₃; 3)*Aluminon + *Cetyltrimethyl- 3)red Al(NO₂)₃•9H₂O; ammonium bromide; Al(NO₃)₃; Al₂(SO₄)₃; 4)Chrome Azurol S; 4)blue AlNH₄(SO₄)₂•12H₂O; 5)Chrome Azurol S + *Cetyltrimethyl- 5)orange AlTl(SO₄)₂•12H₂O; ammonium AlK(SO₄)₂•12H₂O. bromide; 6)Chromazol KS + *Cetylpyridinium 6)violet bromide; 7)*Eriochrome Cyanin R; 7)violet 8)*Eriochrome Cyanin R + *Cetyltrimethylammonium 8)violet bromide; 9)8-Hydroxyquinoline; 9)yellow-green fluorescence 10)Morin and Morin under U.V. 10)intense light; green fluorescence 11)Alizarin sulfonic acid; 11)red 12)Alizarin; 12)deep violet 13)Qunalizarin; 13)red to red- violet 14)Pontachrome blue black R; 14)orange-red fluorescence 15)*Ammonium aurin 15)red lake tricarboxylate (“Aluminon”) 16)Tannin 16)? 17)Chrome Fast Pure Blue B 17)magenta or pink 18)Salicylidene-o-aminophenol 18)yellow- greenish fluorescence 19)Glyoxal bis-(2-hydroxyanil) 19)red Gallium GaCl₂; GaCl₃;GaBr₃. 1)*Pyrocatechol violet + Diphenylguanidine; 1)? (#31) 2)8-Hydroxyquinoline; 2)? 3)1-(2-Pyridylazo)-2-naphthol; 3)? 4)4-(2-Pyridylazo)resorcinol; 4)? 5)Rhodamine B; 5)? 6)*Xylenol Orange; 6)? 7))*Xylenol Orange; + 8- 7)? Hydroxyquinoline; 8)*Potassium ferrocyanide and 8)red-brown *manganese chloride 9)Salicylidene-o-aminophenol + *NaBF₄ 9)yellow fluorescence (UV) 10)Rhodamine S 10)fluorescence (UV) 11)*Gallion 11)blue fluorescence (UV) 12)Lumogallion 12)orange fluorescence (UV) 13)Eriochrome Red B 13)blue fluorescence (UV) Germanium GeF₄•2H₂O 1)Brilliant Green + *Molybdate; 1) #(31) 2)Phenylfluorone; 2) 3)*Ammonium molybdate and 3)blue benzidene; 4)Hydroxyanthroquinone 4)a)yellowish- red, b)orange-wine red c)violet-blue 5)9-Phenyl-2,3,7-trihydroxy-6- 5)pink fluorone 6)Haematoxylin and anion 6)violet to black exchange resin(Amberlite IRA-411) 7)Diphenylcarbazone 7)purple 8)*Ammonium molybdate and 8)evanescent *hydoxylamine hydrochloride blue-green Indium (#49) InCl₃; InI₃; In₂(SO₄)₃ 1)Bromopyrogallol Red; 1)? 2)Chrome Azurol S; 2)? 3)Chrome Azurol S + Cetyltrimethylammonium 3)? bromide 4)Dithizone 4)? 5)8-Hydroxyquinoline 5)? 6)1-(2-Pyridylazo)-2-naphthol 6)? 7)4-(2-Pyridylazo)resorcinol; 7)? 8)Alizarin 8)dark red 9)Quinalizarin 9)violet Tin (#50) H₂SnCl₆•6H₂O; 1)*Pyrocatechol violet 1)? SnBr₂; 2)*Pyrocatechol violet + *Cetyltromethylammonium 2)? SnCl₂; •2H₂O; SnSO₄; bromide Sn(SO₄)₂•2H₂O. 3)Gallein 3)? 4)Phenylfluorone 4)? 5)Toluene-3,4-dithiol + Dispersant 5)? 6)*Mercuric Chloride and aniline 6)brown 7)Cacotheline 7)violet 8)Dimethylglyoxime and *ferric 8)red to clear salts 9)*Sodium Dimethylglyoxime 9)red to clear and *ferric salts 10)Diazine green 10)violet to red 11)2-Benzyl pyridine 11)red 12)*Ammonium 12)yellow to phosphomolybdate deep blue 13)1,2,7- 13)orange Trihydroxyanthroquinone 14)*Anthroquinone-1-azo-4- 14)blue-violet dimethylaniline hydrochloride 15)*Ferric ferricyanide 15)blue 16)Ammonium sulfotellurate 16)black 17)Dithiol 17)red 18)Ammonium 18)blue phosphomolybdate 19)Morin 19)yellow- green fluorescence 20)*Nitronaphthol sulfonic acid 20)blue fluorescence 21)Mercuric chloride and aniline 21)brown 22)Oxidation products of o- 22)geen to blue- aminophenols geen 23)*Phosphomolybdic acid and 23)blue ammonium acetate 24)Glyoxal bis-2-hydroxyanil 24)blue 25)*Sodium rhodizonate 25)violet Antimony SbBr₃; SbCl₃; SbF₃; 1)Brilliant green 1)? (#51) (SbO)KC₄H₄O₆•½H₂O 2)*Brompyrogallol Red 2)? 3)*Silver diethyldithiocarbamate 3)? 4)*Rhodamine B 4)violet or blue 5)*Phosphomolybdic acid 5)blue 6)9-Methyl-2,3,7- 6)red trihydoxyfluorone 7)*Ammonium sulfotellurate 7)black 8)*Mercuric cyanide 8)black or gray 9)*Phosphomolybdic acid 9)blue 10)9-methyl-2,3,7-trihydroxy-6- 10)red fluorone 11)Gallein 11)violet 12)Morin 12)blue green fluorescence (UV) Thallium TlOH; TlCO₂; 1)Brilliant green 1)? (#81) TlClO₄; 2)Dithizone 2)? TlF; TlNO₃; 3)*Rhodamine B 3)? (NH₄)₃Tl6•2H₂O; 4)*Potassium Iodide 4)bright yellow TlP₂O₇; Tl₂SO₄ 5)Benzidene 5)blue 6)*Phosphomolybdic acid + *hydrobromic 6)blue acid 7)*Dipycryl amine (or *sodium 7)red salt) 8)*Ammonium sulfide 8)black-brown 9)*Sodium sulfotellurate 9)brown 10)*Oxidation to trivalent 10)blue thallium in acid solution 11)*Sodium carbonate and 11)black-brown ammonium sulfide 12)*Gold chloride and palladium 12)cinnamon- chloride brown 13)*Alkaline ferricyanide 13)blue-green 14)*Uranyl sulfate 14)fluorescence fade 15)8-Hydroxyquinoline 15)? Lead (#82) Pb(C₂H₃O₂)₂•2H₂O; 1)Dithizone 1)brick red PbBr₂; PzbCL₂; 2)*Sodium 2)? Pb(ClO₄)₂; Pb(NO₃)₂; Diethyldithiocarbamate 3)4-(2-Pyridylazo)resorcinol 3)? 4)*Sodium rhodizonate 4)a)violet(neutral) b)scarlet- red(weak acid 5)*Cadmium-stannous iodide + iodine 5)orange-red 6)Gallocyanine 6)violet 7)Carminic acid 7)violet 8)Benzidine 8)blue 9)Chloranilic acid 9)brown Bismuth Bi(NO₃)₂•5H₂O in dil. 1)Dithizone 1)? (#83) HNO₃; 2)*Pyrocatechol violet 2)? Bi₂(SO₄)₃ in H₂SO₄. 3)*Pyrocatechol violet + Cetyltromethylammonium 3)? bromide 4)*Thiourea 4)? 5)*Xylenol Drange 5)? 6)Cinchonine and *potassium 6)orange-red iodide 7)*Alklali stannate and *lead 7)free salts lead(grey) 8)*Potassium chromium 8)brick red thiocyanate 9)*Alkali stannite + *lead 9)orange or chloride black-brown 10)*Potassium manganese (II) 10)black cyanide 11)Quinoline and *potassium 11)orange-red iodide 12)*Thioacetamide 12)yellow- green

Table 5 represents non-metals, corresponding water soluble salts, resultant inorganic precipitants, and color of the precipitant. TABLE 5 Color of Non-Metals Water Soluble Salts Product PRECIPITANTS. Inorganic precipitants *water soluble Boron (#5) H2BO3; Borates, 1)*Azomethine H 1)? Boranes and 2)*Carminic acid 2)red to blue Borohydrides 3)*Curcumin 3)blue to greenish black 4)*Methylene Blue 4)? 5)*Alizarin S 5)yellowish red to red 6)Purpurin(*hot) 6)orange to wine red 7)Quinalizarin 7)violet to blue 8)Chromotrope 2B 8)greenish-blue 9)Benzoin 9)yellow-green fluorescence 10)*Triphenyltetrazolium 10)red (boranes chloride and borohydrides in soln.) TESTS FOR AMMONIA Nitrogen (as NH₄OH; 1)*Phenol + *Sodium 1)? Ammonia) NH₄C₂H₃O₂; Hypochlorite (#7) NH₄H₂AsO_(4;) 2)*pNitrobenzenediazonium 2)red NH₄AsO₄; chloride NHBr; 3)*Manganese sulfate-*Hydrogen 3)blue (NH₄)₂CO₃•2H₂O; peroxide + Benzidene NH₄HCO₃; NH₄Cl; 4)Litmus 4)blue NH₄ClO₄; 5)*Manganese sulfate and *silver 5)black (NH₄)₂CrO₄; nitrate NH₄CNO; NH₄CN; 6)8-Hydroxyquinoline and *zinc 6)light yellow (NH₄)₂Cr₂O₇; NH₄F; chloride NH₄I; NH₄IO₃; 7)Formation of indophenol blue 7)blue (NH₄)₆Mo₇O₂₄•H₂0; 8)*Silver nitrate and tannin 8)metallic silver NH₄NO₂; NH₄NO₃; 9)Nessler's reagent 9)yellow or (NH₄)₂C₂O₄•H₂O; orange-red NH₄MnO₄; 10)Formation of manganese 10)blue (with (NH₄)₂S₂O₈; dioxide bezidene or (NH₄)₂PtCl₄; tetrabase) (NH₄)₂HPO₄; 11)All other tests are for the 11)See (NH₄)₃PO₄; various water soluble salts of the individual NH₄H₂PO₄; particular elements involved as elements for the (NH₄)₂SO₄; (NH₄)₂S; indicated in the other tables for water soluble (NH₄)₂S₂O₅; that element. salts and the (NH₄)₂SO₃•H₂O; ligands and (NH₄)₂S₂O₃; colors (NH₄)₂SeO₄; produced. NH₄SCN; (NH₄)₂C₄H₄O₆ Phosphorous HPO₃; H₃PO₂; 1)Rhodamine B + *Molybdate + Benzidene 1)blue (#15) H₃PO₃; H₃PO₄; 2)Malachite Green + *Molybdate 2)? H₄P₂O₇; PH₄I; PH₄Cl. 3)*Ammonium molybdate and 3)blue benzidine 4)o-Dianisidine molybdate and 4)brown to blue *hydrazine 5)Qinolinium molybdate 5)yellow Arsenic AsO₃; AsBr₃; AsCl₃; 1)*Silverdiethyldithiocarbamate; 1)? (#33) AsI₃; AsOCl; 2)*Stannous chloride; 2)brownish- H₂AsO₄•½H₂O; black H₂AsO₇. 3)*Silver nitrate + *HCl + Zn 3)a)lemon yellow b)blue to blue-red 4)Kairine(*with HCl) - *ferric 4)red-brown chloride 5)*Ammonium sulfotellurate 5)black 6)Gold chloride 6)metallic gold Selenium SeO₂; H₂SeO₃; 1)3,3′-Diaminobenzene 1)? (#34) H₂SeO₄ 2)*Hydriodic acid 2)red-brown 3)Pyrrole 3)blue 4)Diphenylhydrazine 4)red-violet 5)*Thiourea (solid) 5)red 6)*Ferrous sulfate 6)reduction to Se 7)*Thiourea (10% solution) 7)red-blue fluorescence 8)1,8-Naphthalenediamine 8)brown 9)4-Dimethylamino-1,2- 9)red phenylenediamine 10)4-Methylthio-1,2- 10)blue phenylenediamine Tellurium H₆TeO₆ 1)*Hypophosphorous acid 1)black or grey (#62) 2)* Alkali Stannite 2)black or grey 3)Formation of complex cupric 3)yellow (III) tellurate 4)*Ferrous sulfate and 4)reduction to *phosphoric acid Te 5)*Ammonium polysulfide and 5)black sodium sulfite

Table 6 represents halogens, corresponding water soluble salts, resultant inorganic precipitants, color of the precipitant as well as a references. TABLE 6 PRECIPITANTS. Inorganic precipitants Color of Halogens Water Soluble Salts *water soluble Product Fluorine (#9) Fluorides; 1)Alizarin Fluorine Blue + Lanthanum 1)red to blue Silicofluoride; Boron (III) ion fluoride, etc, 2)Zirconium alizarinate 2)red-violet 3)Zirconium azoarsenate 3)brown to red 4)Thymol blue and zirconium salt 4)blue 5)Xylenol orange and zircomium 5)orange salt Chlorine (#17) HClO3•7H2O; 1)N,N-Dethyl-1.4- 1)? HClO4; Cl2O; ClO2; phenylenediamine and most chlorate 2)*Manganese sulfate and 2)violet compounds *Phosphoric acid Hypochlorites are 3)*Triphenylselenonium salts 3)white tested with 4), 5)&6)., 4)*Safranin(C.I. Basic Red) 4)violet Chlorites use 7) 5)*Thallous hydroxide 5)brown Chlorides use 8) 6)ZnCl₂ + KI + starch 6)blue 7)Nickel hydroxide 7)black 8)Formation of chromyl chloride + diphenylcarbizide 8)violet Bromine HBrO3; and most 1)*Fluorescein 1)pink to red (#35) bromate compounds, 2)Phenol Red 2)? Hypobromites are 3)*Manganese sulfate and 3)red tested with 6), 7), 8). *Sulfuric acid + Benzidene Bromides use 11) 4)*Fuchsin 4)violet 5)*Permolybdate and alpha- 5)orange-red napthaflavone 6)*Safranin(C.I. Basic Red) 6)violet 7)*Thallous hydroxide 7)brown 8)*ZnCl₂ + *KBr + fluorescein 8)red 9)*Sulfanilic acid 9)violet to brown 10)*Phosphomolybdic acid + *sulfosalicylic 10)blue or acid green 11)*KMnO₄ + *CuSO₄ + *iodide + starch 11)blue Iodine (#35) H5IO6; I2O5; and 1)*Hypophosphorous acid + starch 1)blue-blue many iodide and black iodate compounds, 2)*Potassium thiocyanate + starch 2)blue-blue KI, KIO3 etc. black Iodates use 3)*Pyrogallol 3)pink to red 1), 2). 3), 16) 4)Neocuproine *copper(II) 4)? Iodides use 5)*Starch + *KI 5)blue-blue 13), 14), 15)and othe black for free tests as adapted Iodine 6)*Manganeses sulfate and 6)violet *Phosphorous acid + diphenylcarbizide 7)*Manganese salt and tetrabase 7)blue 8)*Fluorescein 8)red-yellow 9))*Fluorescein + *peroxides 9)red-yellow 10)*Starch + *peroxides 10)blue-blue- black 11)*Thallous hydroxide 11)brown 12)*ZnCl₂ + Thiodene 12)blue 13)*Palladium chloride 13)black-brown 14)*Potassium nitrite + starch 14)blue 15)*AgNO₃ 15)yellow 16)p-Aminophenol (for iodates) 16)blue-violet

Table 7 represents other reactants, corresponding water soluble salts, resultant inorganic precipitants, and color of the precipitant. TABLE 7 PRECIPITANTS. Inorganic precipitants Color of Metals Water Soluble Salts *water soluble Product Luminol Hemin 1) *Peroxides 1) Intense blue luminescence Amino Acids Glycocoll, alanine, 1- 1) *Sodium hypochlorite 1) red asparginic acid, (saturated solution) + Fuchsin- tyrosine, diiodotyrosine, sulfurous acid d-arginine, etc, Proteins Egg albumin, 1) *Tetrabromonaphthalein ethyl 1) yellow to hemoglobin, serum ester (potassium salt) blue albumin, casein, any other native protein, etc. Nitrogen (#7) A) Nitrate A) 1) Brucine A) 1) ? 2) Chromotropic acid 2) ? 3) Sulfanilamide + N-(1- 3) ? Naphthyl)ethylenediamine dihydrochloride B) Nitrite B) 1) Sulfanilamide + N-(1- B) 1) ? Naphthyl)ethylenediamine dihydrochloride 2) Sulfanilic acid + 1- 2) ? Naphthylamine C) Nitric Acid C) 1) *Ferrous sulfate (soliD) and C) 1) brown *sulfuric acid ring around crystal 2) Diphenylamine or 2) blue diphenylbenzidene 3) Brucine 3) red D) 1) Alpha-naphthylamine and D) 1) red sulfanilic acid 2) 1,8-Naphthalenediamie 2) orange-red 3) *Iodide and starch 3) blue 4) Chrysean 4) red to dark brown 5) Benzidene 5) yellow to brown 6) *Ferrous sulfate and 6) brown ring *acetic acid around crystal Sulfur (#16) A) Persulfuric acid A) Benzidene A) blue B) Sulfuric acid B) Barium rhodizonate B) red-brown   (soluble sulfate) C) Sulfuric acid (free) C) *Glucose C) charring D) Sulfurous acid D) 1) *Sodium nitroprusside D) 1) red   Sulfates A) 2) *Zinc nitroprusside 2) pink to   Sulfides D) dark red   Sulfites D) 3) Decolorization of malachite 3) decolrization green 4) 2-Benzylpyridene 4) red

Many other reactions as shown in “Qualitative Analysis By Spot Tests”, Feigl (1946 ed.) and newer can also be used. All water soluble substances, whether Inorganic, Organic, Proteinaceous, Enzymatic, etc. Precipitants include water soluble reagents or reagents that can be made water soluble by alkali or acid treatment and that individually or together with another water soluble or dispersible reagent can cause a color to form either as a precipitate or as a color on a filter paper.

Fluorescent indicators are substances which show definite changes in fluorescence with change in pH. A long wavelength ultraviolet lamp is used to show the fluorescence. Referring to table 8 there are shown representative fluorescent indicators which can be used with the present invention. TABLE 8 Color change Name pH range acid to base Indicator solution Benzoflavine −0.3 to 1.7   Yellow to green 1 3,6-Dihydroxyphthalimide   0 to 2.4 Blue to green 1 6.0 to 8.0 Green to yellow/green Eosin (tetrabromofluorescein)   0 to 3.0 Non-fl to green 4, 1% 4-Ethoxyacridone 1.2 to 3.2 Green to blue 1 3,6-Tetramethyldiaminoxanthone 1.2 to 3.4 Green to blue 1 Esculin 1.5 to 2.0 Weak blue to strong blue Anthranilic acid 1.5 to 3.0 non-fl to light 2 (50% ethanol) blue 4.5 to 6.0 Light blue to dark blue 12.5 to 14   Dark blue to non- fl 3-Amino-1-naphthoic acid 1.5 to 3.0 Non-fl to green 2 (as sulfate in 50% ethanol) 4.0 to 6.0 Green to blue 11.6 to 13.0 Blur to non-fl 1-Naphthylamino-6-sulfonamide 1.9 to 3.9 Non-fl to green 3 (also the 1-, 7-)  9.6 to 13.0 Green to non-fl 2-Naphthylamino-6-sulfonamide 7.9 to 3.9 Non-fl to dark 3 blue (also the 2-, 8-)  9.6 to 13.0 Dark blue to non- fl 1-Naphthylamino-5-sulfonamide 2.0 to 4.0 Non-fl to 3 yellow/orange  9.5 to 13.0 Yellow/orange to non-fl 1-Naphothoic acid 2.5 to 3.5 Non-fl to blue 4 Salicyclic acid 2.5 to 4.0 Non-fl to dark 4 (0.5%) blue Phloxin BA extra 2.5 to 4.0 Non-fl to dark 2 (tetrachlorotetrabromofluorescein) blue Erythrosin B 2.5 to 4.0 Non-fl to light 4 (0.2%) (tetraiodofluorescein) green 2-Naphthylamine 2.8 to 4.4 Non-fl to violet 1 Magdala red 3.0 to 4.0 Non-fl to purple p- 3.0 to 4.0 Non-fl to light 3 Aminophenylbenzenesulfonamide blue 2-Hydroxy-3-naphthoic acid 3.0 to 6.8 Blue to green 4 (0.1%) Chromotropic acid 3.1 to 4.4 Non-fl to light 4 (5%) blue 1-Naphthionic acid 3 to 4 Non-fl to blue 4 10 to 12 Blue to yellow- green 1-Naphthylamine 3.4 to 4.8 Non-fl to blue 1 5-Aminosalicylic acid 3.1 to 4.4 Non-fl to light 1 (0.2% fresh) green Quinine 3.0 to 5.0 Blue to weak 1 (0.1%) violet  9.5 to 10.0 Weak violet to non-fl o-Methoxybenzaldehyde 3.1 to 4.4 Non-fl to green 4 (0.2%) o-Phenylenediamine 3.1 to 4.4 Green to non-fl 5 p-Phenylenediamine 3.1 to 4.4 Non-fl to 5 orange/yellow Morin(2′,4′,3,5,7- 3.1 to 4.4 Non-fl to green 6 (0.2%) pentahydroxyflavone   8 to 9.8 Green to yellow/green Thioflavine S 3.1 to 4.4 Dark blue to light 6 (0.2%) blue Fluorescein 4.0 to 4.5 Pink/green to 4 (1%) green Dichlorofluorescein 4.0 to 6.6 Blue green to 1 green β-Methylescletin 4.0 to 6.2 Non-fl to blue 1  9.0 to 10.0 Blue to light green Quininic acid 4.0 to 5.0 Yellow to blue 6 (satd) β-Naphthoquinoline 4.4 to 6.3 Blue to non-fl 3 Resorufin(7-oxyphenoxazone) 4.4 to 6.4 Yellow to orange Acridine 5.2 to 6.6 Green to violet 2 3,6-Dihydroxyxanthone 5.4 to 7.6 Non-fl to 1 blue/violet 5,7-Dihydroxy-4-methylcoumarin 5.5 to 5.8 Light blue to dark blue 3,6-Dihydroxyphthalic acid 5.8 to 8.2 Blue to green 1 dinitrile 1,4-Dihydroxybenzenedisulfonic 6 to 7 Non-fl to light 4 (0.1%) acid blue Luminol 6 to 7 Non-fl to blue 2-Naphthol-6-sulfonic acid 5-7 to 8-9 Non-fl to blue 4 Quinoline 6.2 to 7.2 Blue to Non-fl 6 (satd) 1-Naphthol-5-solfonic acid 6.5 to 7.5 Non-fl to green 6 (satd) Umbelliferone 6.5 to 8.0 Non-fl to blue Magnesium-8-hydroxyquinolinate 6.5 to 7.5 Non-fl to yellow 6 (0.1% in 0.01 M HCl) Orcinaurie 6.5 to 8.0 Non-fl to green 6 (0.03%) Diazo brilliant yellow 6.5 to 7.5 Non-fl to blue Coumaric acid 7.2 to 9.0 Non-fl to green 1 β-Methylumbelliferone >7.0   Non-fl to blue 2 (0.3%) Harmine 7.2 to 8.9 Blue to yellow 2-Naphthol-6,8-disulfonic acid 7.5 to 9.1 Blue to light blue 4 Salicylaldehyde semicarbazone 7.6 to 8.0 Yellow to blue 2 1-Naphthol-2-sulfonic acid 8.0 to 9.0 Dark blue to light 4 blue Salicylaldehyde acetylhydrazone 8.3 Non-fl to 2 green/blue Salicylaldehyde 8.4 Non-fl to 2 thiosemicarbazone blue/green 1-Naphthol-4-solfonic acid 8.2 Dark blue to the 4 light blue Naphthol AS  8.2 to 10.3 Non-fl to 4 yellow/green 2-Naphthol 8.5 to 9.5 Non-fl blue 2 Acridine orange  8.4 to 10.4 Non-fl to yellow/green Orcinsulfonephthalein  8.6 to 10.0 Non-fl to yellow 2-Naphthol-3,6-disulfonic acid 9.0 to 9.5 Dark blue to light 4 blue Ethoxyphenylnaphthostilbazonium  9 to 11 Green to non-fl 1 chloride o-Hydroxyphenylbenzothiazole 9.3 Non-fl to blue 2 green o-Hydrozyphenylbenzoxazole 9.3 Non-fl to 2 blue/violet o-Hydroxyphenylbenzimidazole 9.9 Non-fl to 2 blue/violet Coumarin  9.5 to 10.5 Non-fl to light green 6,7-Dimethoxyisoquinoline-1-  935 to 11.0 Yellow to blue 0.1% in carboxylic acid clycerine/ethanol/water in 2:2:18 ratio 1-Naphthylamino-4-sulfonamide  9.5 to 13.0 dark blue to 3 white/blue

Some of the common acid-base indicators which can be used with the present invention are shown in table 9 with the corresponding pH range. TABLE 9 pH range Color Indicator Minimum Maximum Acid Alkaline Brilliant cresyl blue 0.0 1.0 red-orange blue Methyl violet 0.0 1.6 yellow blue Crystal violet 0.0 1.8 yellow blue Ethyl violet 0.0 2.4 yellow blue Methyl violet 6B 0.1 1.5 yellow blue Cresyl red 0.2 1.8 red yellow 2-(p-Dimethylaminophenylazo) 0.2 1.8 yellow blue pyridine Malachite green 0.2 1.8 yellow blue-green Methyl green 0.2 1.8 yellow blue Cresol red (o- 1.0 2.0 red yellow Cresolsulfonephthalein) Quinaldine red 1.0 2.2 colorless red p-Methyl red 1.0 3.0 red yellow Metanil yello 1.2 2.3 red yellow Pentamethoxy red 1.2 2.3 red-violet colorless Metanil yellow 1.2 2.4 red yellow p-Phenylazodiphenylamine 1.2 2.6 red yellow Thymol blue 1.2 2.8 red yellow (Thymolsulfonephthalein) m-Cresol purple 1.2 2.8 red yellow p-Xylenol blue 1.2 2.8 red yellow Benzopurpurin 4B 1.2 3.8 violet red Tropeolin OO 1.3 3.2 red yellow Orange IV 1.4 2.8 red yellow 4-o-Tolylazo-o-toluidine 1.4 2.8 orange yellow Methyl violet 6B 1.5 3.2 blue violet Phloxine B 2.1 4.1 colorless pink Erythrosine, disodium salt 2.2 3.6 orange red Benxopupurine 4B 2.2 4.2 violet red N,N-dimethyl-p-(m-tolylazo) 2.6 4.8 red yellow aniline 2,4-Dinitrophenol 2.8 4.0 colorless yellow N,N-Dimethyl-p- 2.8 4.4 red yellow phenylazoaniline Methyl yellow 2.9 4.0 red yellow Bromophenol blue 3.0 4.6 yellow blue-violet Tetrabromophenol blue 3.0 4.6 yellow blue Direct purple 3.0 4.6 blue-purple red Congo red 3.1 4.9 blue red Methyl orange 3.1 4.4 red yellow Bromochlorophenol blue 3.2 4.8 yellow blue Ethyl orange 3.4 4.8 red yellow p-Ethoxychrysoidine 3.5 5.5 red yellow Alizarin sodium sulfonate 3.7 5.2 yellow violet α-Naphthyl red 3.7 5.7 red yellow Bromocresol green 3.8 5.4 yellow blue Resazurin 3.8 6.4 orange violet Bromophenol green 4.0 5.6 yellow blue 2,5-Dinitrophenol 4.0 5.8 colorless yellow Methyl red 4.2 6.2 red yellow 2-(p-Dimethylaminophenylazo) 4.4 5.6 red yellow pyridine Lacmoid 4.4 6.2 red blue Azolitmin 4.5 8.3 red blue Litmus 4.5 8.3 red blue Alizarin red S 4.6 6.0 yellow red Chlorophenol red 4.8 6.4 yellow red Cochineal 4.8 6.2 red violet Propyl red 4.8 6.6 red yellow Hematoxylin 5.0 6.0 red blue Bromocresol purple 5.2 6.8 yellow violet Bromophenol red 5.2 7.0 yellow red Chlorophenol red 5.4 6.8 yellow red p-Nirophenol 5.6 6.6 colorless yellow Alizarin 5.6 7.2 yellow red Bromothymol blue 6.0 7.6 yellow blue Indo-oxine 6.0 8.0 red blue Bromophenol blue 6.2 7.6 yellow blue m-Dinitrobenzoylene urea 6.4 8.0 colorless yellow Phenol red 6.4 8.0 yellow red (Phenolsulfonephthalein) Rosolic acid 6.4 8.0 yellow red Brilliant yellow 6.6 7.9 yellow orange Quinoline blue 6.6 8.6 colorless blue Neutral red 6.8 830 red orange Phenol red 6.8 8.4 yellow yellow m-Nitrophenol 6.8 8.6 colorless yellow Cresol red (o- 7.0 8.8 yellow red Cresolsulfonephthalein) α-Naphtholphthalein 7.3 8.8 yellow blue Curcumin 7.4 8.6 yellow red m-Cresol purple (m- 7.4 9.0 yellow violet Cresolsulfonephthalein) Tropeolin OOO 7.6 8.9 yellow rose-red 2,6- 7.8 9.4 yellow red Divanillydenecyclohexanone Thymol blue 8.0 9.6 yellow purple (Thymolsulfonephthalein) p-Xylenol blue 8.0 9.6 yellow blue Turmeric 8.0 10.0 yellow orange Phenolphthalein 8.0 10.0 colorless red o-Cresolphthalein 8.2 9.8 colorless red p-Naphtholphthalein 8.2 10.0 colorless pink Ethyl bis(2,4- 8.4 9.6 colorless blue dimethylphenylacetate) Ethyl bis(2,4-dimtrophenyl 8.4 9.6 colorless blue acetate) α-Naphtholbenzein 8.5 9.8 yellow green Thymolphthalein 9.4 10.6 colorless blue Nile blue A 10.0 11.0 blue purple Alizarin yellow CG 10.0 12.0 yellow lilac Alizarin yellow R 10.2 12.0 yellow orange red Salicyl yellow 10.0 12.0 yellow orange-brown Diazo violet 10.1 12.0 yellow violet Nile blue 10.1 11.1 blue red Curcumin 10.2 11.8 yellow red Malchite green gydrochloride 10.2 12.5 green-blue colorless Methyl blue 10.6 13.4 blue pale violet Brilliant cresyl blue 10.8 12.0 blue yellow Alizarin 11.0 12.4 red purple Nitramine 11.0 13.0 colorless orange-brown Poirier's blue 11.0 13.0 blue violet-pink Tropeolin O 11.0 13.0 yellow orange Indigo carmine 11.4 13.0 blue yellow Sodium indigosulfonate 11.4 13.0 blue yellow Orange G 11.5 14.0 yellow pink 2,4,6-Trinitrotoluene 11.7 12.8 colorless orange 1,3,5-Trinitrobenzene 12.0 14.0 colorless orange 2,4,6 Trinitrobenzoic acid 12.0 13.4 blue violet-pink Clayton yellow 12.2 13.2 yellow amber

Some of the oxidation-reduction indicators which can be used with the present invention are shown in table 10. TABLE 10 Reduction Potential Suitable (30° C.) in Volts at pH Color Change Name pH = 0 pH = 7 range Upon Oxidation Bis(5-bromo-1,10-phenanthroline) 1.41* Red to faint blue ruthenium(II) dinitrate Tris(5-nitro-1,10-phenanthroline) 1.25* Red to faint blue iron(II) sulfate Iron(II)-2,2′,2″-tripyridine sulfate 1.25* Pink to faint blue Tris(4,7-diphenyl01,10- 1.13 (4.6 M Red to faint blue phenanthroline) H₂SO₄)* iron(II) disulfate 0.87 (1.0 M H₂SO₄)* o,m¹-Diphenylaminedicarboxylic 1.12 Colorless to blue acid violet Setopaline 1.06 Yellow to orange (trans) p-Nitrodiphenylamine 1.06 Colorless to violet Tris(1,10-Phenanthroline)-iron(II) 1.06 (1.00 M Red to faint blue sulfate H₂SO₄)* 1.00 (3.0 M H₂SO₄)* 0.89 (6.0 M H₂SO₄)* Setoglaucine O 1.01 Yellow-green to (trans) yellow red Xylene cyanole FF 1.00 Yellow-green to (trans) pink Erioglaucine A 1.00 Green yellow to (trans) bluish red Eriogreen 0.99 Green yellow to (trans) orange Tris(2,2′-bipyridine)-iron(II) 0.97* Red to faint blue hydrochloride 2-Carboxydiphenylamine[N- 0.94 Colorless to pink phenyl-anthranilic acid] Benxidine dihydrochloride 0.92 Colorless to blue o-Toluidine 0.87 Colorless to blue Bis(1,10-phenanthroline)- 0.859 (0.1 M Green to pink osmium(II) H₂SO₄) perchlorate Diphenylamine-4-sulfonate (Na 0.85 Colorless to violet salt) 3,3′-Dimethoxybenzidine 0.85 Colorless to red dihydrochloride [o-dianisidine] Ferrocyphen 0.81 Yellow to violet 4′-Ethoxy-2,4-diaminoazobenzene 0.76 Red to pale yellow N,N-Diphenylbenzidine 0.76 Colorless to violet [o-dianisidine] Colorless to red Ferrocyphen 0.81 Yellow to violet 4′-Ethoxy-2,4-diaminoazobenzene 0.76 Red to pale yellow N,N-Diphenylbenzidine 0.76 Colorless to violet Diphenylamine 0.76 Colorless to violet N,N-Dimethyl-p- 0.76 Colorless to red phenylenediamine Variamine blue B hydrochloride 0.712 0.310 1.5-6.3  Colorless to blue N-Phenyl-1,2,4-benzenetriamine 0.70 Colorless to red Bindschedler's green 0.680 0.224  2-935 2,6-Dichloroindophenol (Na salt) 0.668 0.217 6.3-11.4 Colorless to blue 2,6-Dibromophenolindophenol 0.668 0.216 7.0-12.3 Colorless to blue Brilliant cresyl blue [3-amino-9- 0.583 0.047 0-11 Colorless to blue dimethyl-amino-10- methylphenoxyazine chloride] Iron (II)-tetrapyridine chloride 0.59 Red to faint blue Thionine [Lauth's violet] 0.563 0.064 1-13 Colorless to violet Starch (soluble potato, I₃ present) 0.54 Colorless to blue Gallocyanine (25° C.) 0.021 Colorless to violet Methylene blue 0.532 0.011 1-13 Colorless to blue Nile blue A 0.406 −0.199 1.4-12.3 Colorless to blue [aminonaphthodiethylamino- phenoxazine sulfate] Indigo-5,5′,7,7′-tetrasulfonic acid 0.365 −0.046 <9 Colorless to blue (Na salt) Indigo-5,5′,7-trisulfonic acid (Na 0.332 −0.081 <9 Colorless to blue salt) Indigo-5,5′-disulfonic acid (Na 0.291 −0.125 <9 Colorless to blue salt) Phenosafranine 0.280 −0.252 1-11 Colorless to violet Indigo-5-monosulfonic acid (Na 03262 −0.157 <9 Colorless to blue salt) Safranine T 0324 −03289 1-12 Colorless to violet Bis(dimethylglyoximato)-iron(II) 0.155 6-10 Red to colorless chloride Induline scarlet 0.047 −0.299  3-8.6 Colorless to red Neutral red −0.323 2-11 Colorless to red- violet

FIG. 1 is a perspective view of a preferred embodiment of the indicator of the present invention. For exemplary purposes only, the embodiment of a freeze-thaw indicator will be discussed; however, other embodiments are equally available for use. The device 10 comprises a housing 20 and a capsule 30. Housing 20 defines an interior 22. Interior 22 is bounded by a first surface 24 and a second surface 27 (see FIG. 4). A first reactant 26 is provided within housing 20. Reactant 26 may be located within housing 20 in various ways. For example, reactant 26 can be applied directly to surface 24 or reactant 26 may be applied to a piece of material, such as filter paper, and the material placed inside housing 20. In addition to filter paper, other carriers may also be used with the present invention.

Capsule 30 is located within housing 20. Capsule 30 contains a second reactant 32. Capsule 30 also contains a liquid 34. Liquid 34 is chosen such that it expands upon freezing. A preferred form of liquid 34 is an aqueous solution. Capsule 30 is designed such that it will fracture when liquid 34 freezes. After fracture, reactant 32 can escape capsule 30 to mix with reactant 26. This will not occur, however, while device 10 is in a frozen condition. When device 10 enters a thawed condition, liquid 34 melts/thaws, releasing reactant 32. Reactant 32 then mixes with reactant 26 to form a pigment, indicating that device 10 has made the transition from a frozen condition to a thawed condition. Note that the rigidity of housing 20 can function as a means to protect against crushing of capsule 30.

FIG. 2 is a top view of the freeze-thaw indicator of FIG. 1 indicating a safe condition. Either device 10 has never been frozen or has been frozen and not thawed. One can view first surface 24 through second surface 27. In this condition, surface 24 has a first color 40.

FIG. 3 is a top view of the freeze-thaw indicator of FIG. 1 indicating a transition from a frozen condition to a thawed condition. Device 10 has been frozen and capsule 30 has been fractured. Reactants 32 and 26 have combined to form a pigment. This pigment causes surface 24 to become brilliantly colored to a second color 42, color 42 being different than color 40. Alternatively, if reactant 26 were placed on a piece of material, the material and not necessarily surface 24 will become colored upon mixture of reactants 26, 32. Thus a person can easily determine whether device 10- and therefore any item to which device 10 has been attached—has previously been frozen and thawed.

FIG. 4 is a sectional view of the freeze-thaw indicator of FIG. 1 taken along line 4-4. It is seen that in a preferred embodiment, housing 20 can have two layers 46, 48. At least a portion of layer 46 is transparent, allowing one to view inside housing 20. At least a portion of layer 48 contains an adhesive, allowing device 10 to be coupled to an item to be monitored. One preferred material for housing 20 is foam-board. This material is readily available and inexpensive. Another preferred material for housing 20 is cork. Cork is also readily available and is less crushable than foam-board, which facilitates the manufacturing process. However, housing 20 can be made of any suitable material.

For illustrative purposes only, a preferred manufacturing process will be discussed using cork as the material of housing 20. Device 10 may be manufactured by first providing an amount of cork, preferably in the form of a roll. The cork can then be machined in known fashion to form interior 22. Several interiors 22 can be formed simultaneously. Preferably, the cork has already been treated with an adhesive on each side. Alternatively, adhesive can be applied subsequent to machining interiors 22 in the cork. Once interior 22 has been formed, first reactant 26 can be added. Reactant 26 may be applied to a piece of material, such as paper, and that material placed within interior 22. Capsule 30, which has been manufactured previously and has second reactant 32 and liquid 34 located therein, is then added to interior 22. Transparent layer 46 and adhesive layer 48 can then be added on either side of housing 20, creating a closed volume for interior 22. A preferred method of attachment is lamination. The completed device 10 can then be coupled to an item to be monitored. It should be noted that the order of the steps of the above process can be altered. For example, transparent layer 46 or adhesive layer 48 can be applied to housing 20 prior to adding first reactant 26. In this manner, first reactant 26 can be applied directly to transparent layer 46 or adhesive layer 48.

The reactants discussed above cooperate to form a pigment upon mixing. Use of a pigment as an indicator is better than use of a dye for several reasons. First, pigments are insoluble in water and are solid particles rather than solutions. Dyes completely dissolve in water and are, therefore, solutions. Thus, a smaller amount of each reactant is needed to create a reliable indicator with a pigment than with a dye. This allows an indicator using pigment reactants to use fewer capsules and be smaller than an indicator using dye reactants. As few as a single capsule may be used with the present invention. A smaller indicator may be attached to more items—such as an individual vaccination vial—than are possible with a larger indicator.

Secondly, it is possible to get more “color” into pigments than into dyes. Therefore, pigmented colors tend to be more vibrant and brilliant than dye-based colors. A more brilliant, vibrant color is desirable with a changed condition indicator to increase readability and decrease the likelihood of an erroneous reading. Thus, an indicator with pigment reactants is more reliable than one with dye reactants.

Thirdly, pigment reactants are less likely to react with anything other than the complementary reactant. Thus, an indicator with pigment reactants is more reliable than one with dye reactants.

Finally, the molecules in a dye are spread out and are therefore prone to fading. The molecules in a pigment are spaced closer together and are therefore less prone to fading. If the color in an activated indicator (that is, an indicator that has been cooled below and then heated above the threshold temperature) fades, one might erroneously be lead to believe that the item to which the indicator is attached has been continuously maintained below the threshold temperature. As discussed above, this could lead to grave consequences. Thus, an indicator with pigment reactants is more reliable than one with dye reactants.

Exemplary reactants include water soluble sodium dimethylglyoxime and any water soluble nickel salt, such as nickel chloride. The sodium dimethylglyoxime could be inside the capsule and the nickel salt outside or vice versa. These reactants combine to form a brilliant scarlet, solid, colloidal crystal. These reactants are highly specific and are unlikely to form such a color with other substances. Other pigment reactants may also be used with the indicator of the present invention and other pigment colors may be produced upon a freeze-thaw transition. Once the reactants combine to form a pigment, the pigment remains even if the device is subsequently refrozen.

The capsules that are used with the present invention were manufactured using the equipment described in U.S. Pat. No. 3,389,194, the disclosure of which is incorporated herein in its entirety. Three capsule shell materials were developed. The first shell composition was made of paraffin wax. The second shell composition was made of a paraffin wax blended with a hydrocarbon resin. The third shell composition was made of a paraffin wax blended with a hydrocarbon resin and a polyethylene. Piccolyte S-115 is a preferred hydrocarbon resin. All the capsules were prepared with 5% dimethylglyoxime as a solute in water and the fill to shell ratio ranged from 50/50 to 60/40. Upon testing, the third shell composition was found to result in more completely cracked capsules upon freezing.

A preferred composition comprises 40% paraffin wax, 50% piccolyte S-115 (a hydrocarbon resin), and 10% polyethylene, with a 60% fill to 40% shell ratio. This composition was found to result in proper brittleness at freezing so that assurance of capsule cracking was increased.

The capsule composition may also be altered to provide a high temperature indicator. For example, pure paraffin wax melts at approximately 95° F. Thus, if the capsules are formed of pure paraffin wax, they will melt at approximately 95° F., allowing the reactants to mix and causing a color change. Additives, such as polyethylene, may be added to the paraffin to increase the melting temperature without adversely affecting brittleness. Thus, by selectively adding polyethylene to the paraffin wax and creating the capsules, they may be designed to melt at a predetermined temperature. The indicator can therefore function as a high temperature indicator. Note that this high temperature indicator embodiment may be used in conjunction with the low temperature embodiments discussed above and below, resulting in a dual indicating device.

Although the capsules were filled with a 5% solution of dimethylglyoxime and the co-reactant was located externally to the capsules, the location of the reactants could have been reversed. Also, the capsules could be loaded with a reducing agent such as a 10% solution of sodium bisulfite, or an acid solution, or a base solution and placed upon a colored matrix which when reduced, acidified or alkalinized changes from one color to another.

The threshold temperature at which the device of the present invention will indicate a changed condition may be varied by varying the composition of liquid 34. By adding and varying the composition of sodium dimethylglyoxime within liquid 34 within capsules 30, capsules 30 may be made to fracture at temperatures as low as −26° C. This allows indicator 10 to be used with items that should be maintained at a temperature below freezing, such as frozen vaccines.

Varying the composition of sodium dimethylglyoxime within liquid 34 may be accomplished by adding salt (NaCl) to water (H₂O) and encapsulating the mixture within capsule 30. By controlling the amount of salt, according to the well-known Arrenhius equation, the freezing point of liquid 34 can be adjusted to freeze, and therefore fracture capsule 30, at any temperature between 0° C. and approximately −26° C. An unexpected advantage of the salt addition is that the intensity of the color change that occurs when nickel-dimethylglyoxime pigment is formed is greater than when no additional salt other than the sodium dimethylglyoxime is present in the aqueous solution 34.

Other substances, such as propylene glycol, glycerin, magnesium chloride, calcium chloride and/or other salts, may be used to lower the freezing point of liquid 34. However, sodium chloride (NaCl) is preferred because it is inexpensive and non-toxic. Additionally, while other metallic salts might adversely interfere with the reaction, sodium chloride essentially does not, and, if anything, enhances the reaction. This is probably due to the common ion (sodium or chloride or both) effect. Substances such as alcohol, acetone, propylene glycol, and glycerin are not preferred for use in altering the freezing temperature of liquid 34 since they may soften the shell of capsule 30 if a wax composition is used.

Table 11, which was taken from “Lange's Handbook of Chemistry,” Revised Tenth Edition (1966), illustrates the percent salt in an aqueous solution and the lowered freezing point resulting therefrom. TABLE 11 % NaCl Spec. Gravity Freezing Point by weight 15° C. (59° F.) ° C. ° F.  0 1.000 0.00 32.0  1 1.007 −0.58 31.0  2 1.014 −1.13 30.0  3 1.021 −1.72 28.9  4 1.028 −2.35 27.8  5 1.036 −2.97 26.7  6 1.043 −3.63 25.5  7 1.051 −4.32 24.2  8 1.059 −5.03 22.9  9 1.067 −5.77 21.6 10 1.074 −6.54 20.2 11 1.082 −7.34 18.8 12 1.089 −8.17 17.3 13 1.097 −9.03 15.7 14 1.104 −9.94 14.1 15 1.112 −10.88 12.4 16 1.119 −11.90 10.6 17 1.127 −12.93 8.7 18 1.135 −14.03 6.7 19 1.143 −15.21 4.6 20 1.152 −16.46 2.4 21 1.159 −17.78 0.0 22 1.168 −19.19 −2.5 23 1.176 −20.69 −5.2 23.3 (E) 1.179 −21.13 −6.0 24 1.184 −17.0* 1.4* 25 1.193 −10.4* 13.3* 26 1.201 −2.3* 27.9* 26.3 1.203 0.0* 32.0* *Saturation temperatures of sodium chloride dihydrate; at these temperatures NaCl₂H₂O separates leaving the brine of the eutectic composition (E).

Color-coding may be used to differentiate the threshold temperature of the capsules. For example, one set of capsules 30 may be made with the natural color of the standard formulation discussed above. Another set of capsules may be prepared with salt added to the liquid 34 to adjust to the required threshold temperature, these capsules 30 being dyed light blue to distinguish them. No other change to the indicators 10 is necessary, and the same manufacturing process may be used.

Alternatively, the composition of liquid 34 could be varied such that it freezes at a temperature above 0° C. Thus, exemplary threshold temperatures include below the freezing temperature, at the freezing temperature, and above the freezing temperature. It may be desirable to determine whether capsules 30 are suitable for use prior to manufacturing device 10. To do this, one can immerse capsules 30 in a solution containing a complementary reactant to that included within capsule 30. For example, if sodium dimethylglyoxime is used as the reactant within capsules 30, the solution can contain a solution of nickel chloride. A preferred solution contains 5% nickel chloride in water, to which 20% by weight glycerol is added. If a capsule is already fractured, and therefore unsuitable for use, the reactants will combine to produce a brilliant pigment when the capsule is immersed in the solution. Those capsules that do not produce a color change are suitable for use and may be separated for subsequent use in the present invention.

During testing of the present invention, it was discovered that capsules tested according to the above process retained a coating of reactant on the outer surface of the capsule 30 when removed from the solution and allowed to dry. When the capsules 30 that tested as good for use were subsequently fractured, the reactant inside capsule 30 combined with the reactant on the outer surface of capsule 30 to form a brilliant pigment. This indicates that capsules 30 may be coated with the second reactant and used in the device 10 of the present invention, without the need of separately including a reactant in the interior 22 of housing 20.

FIG. 5 is a sectional view of another preferred embodiment of the freeze-thaw indicator of the present invention. Device 110 comprises a housing 20 and a capsule 30 (described above). Housing 20 includes layers 46, 48 and defines a volume 22. Capsule 30 has a first reactant 26 and a liquid 34 included therein. Liquid 34 is chosen such that it expands upon freezing. Device 110 further comprises a piece of material 120. Material 120 may be impregnated with second reactant 32. Alternatively, reactant 32 may be topically applied to material 120. Material 120 may take any desired form, as long as it is able to host reactant 32. Preferred forms of material 120 include, but are not limited to, paper (such as filter paper) and cotton. Upon freezing and expansion of liquid 34, capsule 30 fractures. Upon subsequent melting or thawing of liquid 34, reactant 26 is released from capsule 30 such that it contacts material 120 and reactant 32. Reactants 26 and 32 cooperate to form a brilliant pigment, notifying a viewer that device 110- and therefor any item to which device 110 has been attached—has previously been cooled below and then heated above the threshold temperature.

FIG. 6 is a sectional view of another preferred embodiment of the changed condition indicator of the present invention. Device 210 comprises a capsule 30 (described above) and a blister pack 220. Blister packs 220 are known and commonly used to package, for example, over-the-counter medications. Blister pack 220 includes a cover 222 and a backing 224. Cover 222 is substantially transparent, allowing one to view inside device 210. Backing 224 includes a first surface 225. An adhesive may be applied to surface 225 to couple device 210 to an item to be monitored. A first reactant is included within capsule 30. A second reactant may be applied to a piece of material 230, which is enclosed along with capsule 30 within blister pack 220. Alternatively, the second reactant may be applied to a second surface 226 of backing 224 using, for example, an adhesive such as latex. A preferred adhesive is polyvinyl acetate latex; a preferred reactant-latex mix includes 10-20% by volume latex. Alternatively, the second reactant may be applied to the outer surface of capsule 30. With the latter two alternatives, material 230 is not required. As discussed above, when capsule 30 fractures upon freezing and subsequently thaws, the reactants combine to form a pigment, notifying an observer that the item to which device 210 is attached has experienced a changed condition.

FIG. 7 is a sectional view of another preferred embodiment of the freeze-thaw indicator of the present invention. Device 310 comprises a housing 320 and a capsule 30. Housing 320 is substantially cylindrical and has an outer surface 330. The longitudinal ends of housing 320 may be crimped or sealed in any known manner. Device 310 may be attached to an item to be monitored in known manner, such as by applying an adhesive to surface 330. The reactants are included in any manner described above. Upon a freeze-to-thaw transition, the reactants mix as described above to produce a vibrant color, allowing one to easily determine whether the item to which device 310 is attached has been previously frozen and thawed.

FIG. 8 is a sectional view of another preferred embodiment of the changed condition indicator of the present invention. The device 410 of FIG. 8 is similar to the device 310 of FIG. 7, but includes an additional housing 420. Housing 420 and housing 320 cooperate to define a volume 430. Volume 430 functions as an air space, which is an insulator. This insulation may prevent obtaining a premature indication of a thaw condition. The amount of insulation can be varied as desired by varying the relative diameters of the housings 320, 420 (which therefore will vary the size of volume 430).

A preferred method of including the second reactant for the embodiments of FIGS. 7 and 8 is to prepare a reactant-latex mix as described above. The reactant-latex mix can then be drawn into the housing 320, such as by suction. The reactant-latex mix can then be removed from housing 320, such as by draining due to gravity. A film of the mix will remain on an inner surface 340 of housing 320. During testing, it was discovered that a film formed accordingly contained enough reactant to produce a vibrant color change upon a changed condition. This process worked on a housing made of polyethylene, which is known not to be easily coated. This process also worked on a paraffin wax coating of the capsules themselves. This process is fast, inexpensive, and readily adaptable to devices of virtually any size.

By changing the reactants, the device of the present invention may also be used as a time-temperature indicator. For example, by coating the housing with a gelatin-immobilized urease (an enzyme that breaks down urea to ammonia and carbon dioxide) together with a mixture of pH indicators and filling the capsule with a urea solution, upon fracture of the capsule the reactants will mix. This will allow the urease to produce the breakdown products of urea in response to time and temperature according to the Arrenhius equation. As these products (ammonia and carbon dioxide) accumulate in response to time, temperature, or both, the pH of the coating will change. This change in pH will result in a color change based on the indicators chosen. The concentration of the urea solution can be varied in concentration to allow for various time or temperature scenarios. Note that the capsule can be fractured by either external or internal pressure. Other chemical combinations may also be used.

By providing a relatively flexible (or at least less rigid) housing 20, 220, 320, 420, a user can initiate the process by manually fracturing capsule 30. This can be done, for example, by squeezing housing 20, 220, 320, 420. The device 10, 110, 210, 310, 410 can then be attached to an item to be monitored. By doing so, an observer can determine how long the item being monitored has been in its current condition (for example, held at room temperature). Note that by providing a less rigid housing 20, 220, 320, 420, there is no need to freeze the device 10, 110, 210, 310, 410 prior to use. Device 10, 110, 210, 310, 410, when used as a time-temperature indicator, is of the same design and manufacturing as described above with respect to the changed condition indicators.

Numerous modifications and alternative embodiments of the invention will be apparent to those skilled in the art in view of the foregoing description. For example, the received signal can be delay rather than the reference sequence. Accordingly, this description is to be construed as illustrative only and is for the purpose of teaching those skilled in the art the best mode of carrying out the invention. Details of the structure may be varied substantially without departing from the spirit of the invention and the exclusive use of all modifications, which come within the scope of the appended claim, is reserved. 

1. A device for indicating a transition across a threshold temperature comprising: a housing having a first surface, at least a portion of said first surface being of a first color; a first reactant located within said housing; and a capsule containing a liquid and a second reactant, said capsule being located within said housing; whereby said liquid freezes at the threshold temperature and expands upon freezing; wherein said first and said second reactants cooperate to produce a pigment upon mixing; and wherein said first reactant and said second reactant are a weak acid-strong base.
 2. A device for indicating a transition across a threshold temperature comprising: a housing having a first surface, at least a portion of said first surface being of a first color; a first reactant located within said housing; and a capsule containing a liquid and a second reactant, said capsule being located within said housing; whereby said liquid freezes at the threshold temperature and expands upon freezing; wherein said first and said second reactants cooperate to produce a pigment upon mixing; and wherein said first reactant and said second reactant are a strong acid-weak base.
 3. A device for indicating a transition from below a threshold temperature to above the threshold temperature, comprising: a housing having a first surface, at least a portion of said first surface being of a first color; a first reactant located within said housing; and a capsule containing a liquid and a second reactant, said capsule being located within said housing; whereby said microcapsule melts at the threshold temperature; wherein said first and said second reactants cooperate to produce a pigment upon mixing.
 4. The device as recited in claim 3 wherein said first reactant and said second reactant are a weak acid-strong base.
 5. The device as recited in claim 3 wherein said first reactant and said second reactant are a strong acid-weak base.
 6. The device as recited in claim 3 wherein said first reactant and said second reactant are fluorescent.
 7. The device as recited in claim 3 wherein said first reactant and said second reactant are time reactant. 